Roget's Thesaurus of English Words and Phrases by Peter Mark Roget

(concavity) 252. hollow, pit, shaft, well, crater; gulf &c 198; bowels of the earth, botttomless pit†, hell. soundings, depth of water, water, draught, submersion; plummet, sound, probe; sounding rod, sounding line; lead. bathymetry. [instrument to measure depth] sonar, side-looking sonar; bathometer†. V. be deep &c adj.; render deep &c adj.; deepen. plunge &c 310; sound, fathom, plumb, cast the lead, heave the lead, take soundings, make soundings; dig &c (excavate) 252. Adj. deep, deep seated; profound, sunk, buried; submerged &c 310; subaqueous, submarine, subterranean, subterraneous, subterrene†; underground. bottomless, soundless, fathomless; unfathomed, unfathomable; abysmal; deep as a well; bathycolpian†; benthal†, benthopelagic†; downreaching†, yawning. knee deep, ankle deep. Adv. beyond one's depth, out of one's depth; over head and ears; mark twine, mark twain.