A flat is an apartment. If a girl invites you up to her flat, she's not trying to squash you, she's inviting you over. And she's probably from England, because flat is much more common in British than American English.

Geometrically, something flat is an even, level plane, like Kansas relative to the Rocky Mountains, or the cargo area of a flatbed truck. As an adjective, flat means "less than lively." A flat soda has no bubbles. If your speech falls flat, no one was excited. If you get mugged you might choose to lie flat on the ground. A flat note is just below the right pitch. And if you're cooking is flat, it's boring.

Definitions of flat
  1. adjective
    having a surface without slope, tilt in which no part is higher or lower than another
    “a flat desk”
    “skirts sewn with fine flat seams”
    synonyms: level, plane
    being level or straight or regular and without variation as e.g. in shape or texture; or being in the same plane or at the same height as something else (i.e. even with)
  2. adjective
    horizontally level
    “a flat roof”
    parallel to or in the plane of the horizon or a base line
  3. adjective
    flattened laterally along the whole length (e.g., certain leafstalks or flatfishes)
    synonyms: compressed
    of relatively small extent from one surface to the opposite or in cross section
  4. adjective
    having a relatively broad surface in relation to depth or thickness
    flat computer monitors”
    planar, two-dimensional
    involving two dimensions
  5. adjective
    stretched out and lying at full length along the ground
    “found himself lying flat on the floor”
    synonyms: prostrate
    not upright in position or posture
  6. noun
    a level tract of land
    “the salt flats of Utah”
    see moresee less
    alluvial flat, alluvial plain
    a flat resulting from repeated deposits of alluvial material by running water
    salt flat, salt plain
    a flat expanse of salt left by the evaporation of a body of salt water
    type of:
    champaign, field, plain
    extensive tract of level open land
  7. noun
    a suite of rooms usually on one floor of an apartment house
    synonyms: apartment
    see moresee less
    show 11 types...
    hide 11 types...
    bedsit, bedsitter, bedsitting room
    a furnished sitting room with sleeping accommodations (and some plumbing)
    cold-water flat
    an apartment without modern conveniences
    duplex, duplex apartment
    an apartment having rooms on two floors that are connected by a staircase
    efficiency apartment
    a furnished apartment with a kitchenette and bathroom
    a tiny flat
    maisonette, maisonnette
    a self-contained apartment (usually on two floors) in a larger house and with its own entrance from the outside
    an apartment located on the top floors of a building
    railroad flat
    an apartment whose rooms are all in a line with doors between them
    studio, studio apartment
    an apartment with a living space and a bathroom and a small kitchen
    rooms, suite
    apartment consisting of a series of connected rooms used as a living unit (as in a hotel)
    walk-up, walk-up apartment
    an apartment in a building without an elevator
    type of:
    housing, living accommodations, lodging
    structures collectively in which people are housed
  8. noun
    a shallow box in which seedlings are started
    see moresee less
    type of:
    a (usually rectangular) container; may have a lid
  9. noun
    freight car without permanent sides or roof
    synonyms: flatbed, flatcar
    see moresee less
    type of:
    freight car
    a railway car that carries freight
  10. noun
    scenery consisting of a wooden frame covered with painted canvas; part of a stage setting
    see moresee less
    coulisse, wing flat
    a flat situated in the wings
    teaser, tormenter, tormentor
    a flat at each side of the stage to prevent the audience from seeing into the wings
    type of:
    scene, scenery
    the painted structures of a stage set that are intended to suggest a particular locale
  11. adverb
    with flat sails
    “sail flat against the wind”
  12. adjective
    lacking stimulating characteristics; uninteresting
    “a flat joke”
    synonyms: bland
    unexciting, unstimulating
    not stimulating
  13. adjective
    lacking taste or flavor or tang
  14. adjective
    having lost effervescence
    “a flat cola”
    not effervescent
  15. adjective
    commercially inactive
    flat sales for the month”
    “prices remained flat
    “a flat market”
    (pathology) not progressing or increasing; or progressing slowly
  16. adjective
    not reflecting light; not glossy
    flat wall paint”
    synonyms: mat, matt, matte, matted
    emitting or reflecting very little light
  17. noun
    a deflated pneumatic tire
    synonyms: flat tire
    see moresee less
    type of:
    pneumatic tire, pneumatic tyre
    a tire made of reinforced rubber and filled with compressed air; used on motor vehicles and bicycles etc
  18. adjective
    not modified or restricted by reservations
    “a flat refusal”
    synonyms: categoric, categorical, unconditional
    not limited or restricted
  19. adjective
    lacking the expected range or depth; not designed to give an illusion or depth
    “a flat two-dimensional painting”
    synonyms: 2-dimensional, two-dimensional
    having or involving or marked by several dimensions or aspects
  20. adjective
    sounded or spoken in a tone unvarying in pitch
    synonyms: monotone, monotonic, monotonous
    characterized by lack of variation in pitch, tone, or volume
  21. adjective
    lacking contrast or shading between tones
    see moresee less
    having sharp differences between black and white
  22. adverb
    in a forthright manner; candidly or frankly
    “came out flat for less work and more pay”
    synonyms: directly, straight
    see moresee less
    indirectly, obliquely
    not in a forthright manner
  23. adjective
    (of a musical note) lowered in pitch by one chromatic semitone
    “B flat
    see moresee less
    (of a musical note) being neither raised nor lowered by one chromatic semitone
    (of a musical note) raised in pitch by one chromatic semitone
    show more antonyms...
  24. noun
    a musical notation indicating one half step lower than the note named
    see moresee less
    double flat
    a musical notation of two flats in front of a note indicating that it is to be lowered by two semitones
    type of:
    musical notation
    (music) notation used by musicians
Word Family

Test prep from the experts

Boost your test score with programs developed by Vocabulary.com’s experts.

  • Proven methods: Learn faster, remember longer with our scientific approach.
  • Personalized plan: We customize your experience to maximize your learning.
  • Strategic studying: Focus on the words that are most crucial for success.


  • Number of words: 500+
  • Duration: 8 weeks or less
  • Time: 1 hour / week


  • Number of words: 500+
  • Duration: 10 weeks or less
  • Time: 1 hour / week


  • Number of words: 700+
  • Duration: 10 weeks
  • Time: 1 hour / week