expansive
hollow
abysmal
abyssal
boat-shaped
boatlike
bottomless
bowl-shaped
bowllike
cavelike
commodious
concave
concaved
craterlike
cup-shaped
cupped
cymbiform
deep as hell
dish-shaped
dished
dishing
dishlike
fathomless
funnel-breasted
funnel-chested
funnel-shaped
gaping
hollowed
incurved
incurving
incurvous
infundibular
infundibuliform
navicular
naviform
plumbless
plunging
retiring
retreating
reverberant
saucer-shaped
scaphoid
scyphate
sepulchral
soundless
spoonlike
sunk
sunken
unfathomable
unfathomed
airless
capacious
circular
dank
domed
featureless
high-ceilinged
lightless
murky
outer
second-floor
semicircular
shadowy
spacious
stuffy
subterranean
windowless