An invertebrate is an animal without a backbone. Invertebrate animals include fruit flies and sea sponges.

Your backbone allows you to stand up straight, and it also allows you to be grouped with the other vertebrates: animals with backbones. Invertebrates are the opposite: they have no backbone. These are the two major groups of animals. Also, this word is used for people who are spineless in the sense of having no courage. You could say a coward acts in an invertebrate way. Whether it's a backbone-free animal or a courage-free person, all invertebrates lack spines.

Definitions of invertebrate

n any animal lacking a backbone or notochord; the term is not used as a scientific classification

show 65 types...
hide 65 types...
invertebrate having jointed limbs and a segmented body with an exoskeleton made of chitin
any of various invertebrate animals resembling a plant such as a sea anemone or coral or sponge
parazoan, poriferan, sponge
primitive multicellular marine animal whose porous body is supported by a fibrous skeletal framework; usually occurs in sessile colonies
cnidarian, coelenterate
radially symmetrical animals having saclike bodies with only one opening and tentacles with stinging structures; they occur in polyp and medusa forms
comb jelly, ctenophore
biradially symmetrical hermaphroditic solitary marine animals resembling jellyfishes having for locomotion eight rows of cilia arranged like teeth in a comb
any of numerous relatively small elongated soft-bodied animals especially of the phyla Annelida and Chaetognatha and Nematoda and Nemertea and Platyhelminthes; also many insect larvae
borer, woodborer
any of various insects or larvae or mollusks that bore into wood
minute aquatic multicellular organisms having a ciliated wheel-like organ for feeding and locomotion; constituents of freshwater plankton
mollusc, mollusk, shellfish
invertebrate having a soft unsegmented body usually enclosed in a shell
hermaphrodite wormlike animal living in mud of the sea bottom
bryozoan, moss animal, polyzoan, sea mat, sea moss
sessile aquatic animal forming mossy colonies of small polyps each having a curved or circular ridge bearing tentacles; attach to stones or seaweed and reproduce by budding
sessile mossy aquatic animal having the anus of the polyp outside the crown of tentacles
any of various moss-like aquatic animals usually forming branching colonies; each polyp having a both mouth and anus within a closed ring of tentacles
Symbion pandora
only known species of Cycliophora; lives symbiotically attached to a lobster's lip by an adhesive disk and feeding by means of a hairy mouth ring; its complex life cycle includes asexual and sexual phases
brachiopod, lamp shell, lampshell
marine animal with bivalve shell having a pair of arms bearing tentacles for capturing food; found worldwide
peanut worm, sipunculid
small unsegmented marine worm that when disturbed retracts its anterior portion into the body giving the appearance of a peanut
marine invertebrates with tube feet and five-part radially symmetrical bodies
an extinct arthropod that was abundant in Paleozoic times; had an exoskeleton divided into three parts
arachnid, arachnoid
air-breathing arthropods characterized by simple eyes and four pairs of legs
general term for any terrestrial arthropod having an elongated body composed of many similar segments: e.g. centipedes and millipedes
Scutigerella immaculata, garden centipede, garden symphilid, symphilid
minute arthropod often infesting the underground parts of truck-garden and greenhouse crops
an arthropod of the division Tardigrada
chiefly nocturnal predacious arthropod having a flattened body of 15 to 173 segments each with a pair of legs, the foremost pair being modified as prehensors
millepede, milliped, millipede
any of numerous herbivorous nonpoisonous arthropods having a cylindrical body of 20 to 100 or more segments most with two pairs of legs
pycnogonid, sea spider
any of various small spiderlike marine arthropods having small thin bodies and long slender legs
Merostomata, class Merostomata
used in some classifications; includes the orders Xiphosura and Eurypterida
Limulus polyphemus, Xiphosurus polyphemus, horseshoe crab, king crab
large marine arthropod of the Atlantic coast of North America having a domed carapace that is shaped like a horseshoe and a stiff pointed tail; a living fossil related to the wood louse
Asian horseshoe crab
horseshoe crab of the coast of eastern Asia
large extinct scorpion-like arthropod considered related to horseshoe crabs
pentastomid, tongue worm
wormlike arthropod having two pairs of hooks at the sides of the mouth; parasitic in nasal sinuses of mammals
glass sponge
a siliceous sponge (with glassy spicules) of the class Hyalospongiae
one of two forms that coelenterates take (e.g. a hydra or coral): usually sedentary with a hollow cylindrical body usually with a ring of tentacles around the mouth
medusa, medusan, medusoid
one of two forms that coelenterates take: it is the free-swimming sexual phase in the life cycle of a coelenterate; in this phase it has a gelatinous umbrella-shaped body and tentacles
any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans
any of various usually free-swimming marine coelenterates having a gelatinous medusoid stage as the dominant phase of its life cycle
hydroid, hydrozoan
colonial coelenterates having the polyp phase dominant
actinozoan, anthozoan
sessile marine coelenterates including solitary and colonial polyps; the medusoid phase is entirely suppressed
delicately iridescent thimble-shaped ctenophores
ctenophore have long tentacles and flattened body
sea gooseberry
ctenophore having a rounded body with longitudinal rows of cilia
Cestum veneris, Venus's girdle
ctenophore having a ribbon-shaped iridescent gelatinous body
helminth, parasitic worm
worm that is parasitic on the intestines of vertebrates especially roundworms and tapeworms and flukes
a larva of a woodborer
acanthocephalan, spiny-headed worm
any of various worms living parasitically in intestines of vertebrates having a retractile proboscis covered with many hooked spines
arrowworm, chaetognath
any worm of the Chaetognatha; transparent marine worm with horizontal lateral and caudal fins and a row of movable curved spines at each side of the mouth
flatworm, platyhelminth
parasitic or free-living worms having a flattened body
nemertean, nemertine, proboscis worm, ribbon worm
soft unsegmented marine worms that have a threadlike proboscis and the ability to stretch and contract
beard worm, pogonophoran
slender animal with tentacles and a tubelike outer covering; lives on the deep ocean bottom
nematode, nematode worm, roundworm
unsegmented worms with elongated rounded body pointed at both ends; mostly free-living but some are parasitic
annelid, annelid worm, segmented worm
worms with cylindrical bodies segmented both internally and externally
burrowing marine mollusk
gastropod, univalve
a class of mollusks typically having a one-piece coiled shell and flattened muscular foot with a head bearing stalked eyes
chiton, coat-of-mail shell, polyplacophore, sea cradle
primitive elongated bilaterally symmetrical marine mollusk having a mantle covered with eight calcareous plates
bivalve, lamellibranch, pelecypod
marine or freshwater mollusks having a soft body with platelike gills enclosed within two shells hinged together
cephalopod, cephalopod mollusk
marine mollusk characterized by well-developed head and eyes and sucker-bearing tentacles
any mainly aquatic arthropod usually having a segmented body and chitinous exoskeleton
onychophoran, peripatus, velvet worm
any of numerous velvety-skinned wormlike carnivorous animals common in tropical forests having characteristics of both arthropods and annelid worms
small air-breathing arthropod
an insect or other arthropod between molts
sea star, starfish
echinoderms characterized by five arms extending from a central disk
brittle star, brittle-star, serpent star
an animal resembling a starfish with fragile whiplike arms radiating from a small central disc
basket fish, basket star
any starfish-like animal of the genera Euryale or Astrophyton or Gorgonocephalus having slender complexly branched interlacing arms radiating from a central disc
sea urchin
shallow-water echinoderms having soft bodies enclosed in thin spiny globular shells
primitive echinoderms having five or more feathery arms radiating from a central disk
holothurian, sea cucumber
echinoderm having a flexible sausage-shaped body, tentacles surrounding the mouth and tube feet; free-living mud feeders
Type of:
animal, animate being, beast, brute, creature, fauna
a living organism characterized by voluntary movement

adj lacking a backbone or spinal column

“worms are an example of invertebrate animals”
having a backbone or spinal column

Sign up, it's free!

Whether you're a student, an educator, or a lifelong learner, can put you on the path to systematic vocabulary improvement.