Antonyms of adj buoyant

2 senses of buoyant

Sense 1
buoyant, floaty -- (tending to float on a liquid or rise in air or gas; "buoyant balloons"; "buoyant balsawood boats"; "a floaty scarf")

INDIRECT (VIA light) -> heavy -- (of comparatively great physical weight or density; "a heavy load"; "lead is a heavy metal"; "heavy mahogany furniture")

Sense 2
buoyant, chirpy, perky -- (characterized by liveliness and lightheartedness; "buoyant spirits"; "his quick wit and chirpy humor"; "looking bright and well and chirpy"; "a perky little widow in her 70s")

INDIRECT (VIA cheerful) -> depressing, cheerless, uncheerful -- (causing sad feelings of gloom and inadequacy; "the economic outlook is depressing"; "something cheerless about the room"; "a moody and uncheerful person"; "an uncheerful place")

Similarity of adj buoyant

2 senses of buoyant

Sense 1
buoyant, floaty -- (tending to float on a liquid or rise in air or gas; "buoyant balloons"; "buoyant balsawood boats"; "a floaty scarf")
       => light (vs. heavy) -- (of comparatively little physical weight or density; "a light load"; "magnesium is a light metal--having a specific gravity of 1.74 at 20 degrees C")

Sense 2
buoyant, chirpy, perky -- (characterized by liveliness and lightheartedness; "buoyant spirits"; "his quick wit and chirpy humor"; "looking bright and well and chirpy"; "a perky little widow in her 70s")
       => cheerful (vs. depressing) -- (being full of or promoting cheer; having or showing good spirits; "her cheerful nature"; "a cheerful greeting"; "a cheerful room"; "as cheerful as anyone confined to a hospital bed could be")