9
colorless(adjective, dull, simple, soft, obscure)
9
decumbent(adjective, smooth, level, small, down)
9
dim(adjective, dull, quiet, light, soft)
9
empty(adjective, smooth, poor, level, trivial)
9
firm(noun, adjective, change, certain, definite)
9
heavy(adjective, dull, ordinary, dry, boring)
9
ho-hum(adjective, dull, weak, smooth, simple)
9
lackluster(adjective, dull, light, simple, excite)
9
mild(adjective, dull, quiet, weak, kind)
9
needy(adjective, poor, low, informal, exhausted)
9
ordinary(adjective, dull, set, simple, plain)
9
out-and-out(adjective, complete, total, big, limited)
9
planar(adjective, smooth, informal, level, even)
9
poor(adjective, weak, low, thin, delicate)
9
positive(adjective, complete, informal, energetic, big)
9
procumbent(adjective, smooth, level, down, lying)
9
slow(adjective, dullness, weariness, physical inertness)
9
sluggish(adjective, calm, dull, quiet, slow)
9
trite(adjective, dull, set, hard, simple)
9
unpalatable(adjective, good, dull, weak, nasty)
10 years ago|55k views|share |citing 
APASmart Define. (2016). flat thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/flat/thesaurus/synonyms
ChicagoSmart Define. 2016. "flat thesaurus" https://smartdefine.org/flat/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2016, flat thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/flat/thesaurus/synonyms>.
MLASmart Define. "flat thesaurus" 1 March 2016. Web. 20 September 2026. <https://smartdefine.org/flat/thesaurus/synonyms>