A leech is a kind of worm that feeds by sucking blood from other animals. You might find yourself needing to pull a leech off your leg after swimming in a lake.

Because leeches are parasites, it's common for people to use the word as a metaphor for someone who sponges off of other people. If you have a friend who is always borrowing money but never pays it back, and who is known for requesting favors without granting them in return, you can call him a leech. The blood-sucking leech was once commonly used by doctors who treated patients by "bleeding" them, a practice that's still occasionally used in medicine today.

Definitions of leech
  1. noun
    carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end
    synonyms: bloodsucker, hirudinean
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    Hirudo medicinalis, medicinal leech
    large European freshwater leech formerly used for bloodletting
    any of several large freshwater leeches
    type of:
    annelid, annelid worm, segmented worm
    worms with cylindrical bodies segmented both internally and externally
  2. noun
    a follower who hangs around a host (without benefit to the host) in hope of gain or advantage
    synonyms: parasite, sponge, sponger
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    type of:
    a person who accepts the leadership of another
  3. verb
    draw blood
    synonyms: bleed, phlebotomise, phlebotomize
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    type of:
    care for, treat
    provide treatment for
Word Family

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