ETYM Latin abyssus a bottomless gulf, from Greek for bottomless; a priv. + byssos depth, bottom.
(Irregular plural: abysses).
A bottomless gulf or pit; SYN. abysm.
Any unfathomable (or apparently unfathomable) cavity or chasm or void extending below (often used figuratively)
chasm / kæzəm /
ETYM Latin chasma, Greek, from chainein to gape, to open wide. Related to Chaos.
A deep opening in the earth's surface.
gulf / ɡəlf /
ETYM French golfe, Italian golfo, from Greek kolpos bosom, bay, gulf.
1. A deep wide chasm.
2. An arm of a sea or ocean partly enclosed by land; larger than a bay.
3. An unbridgeable disparity (as from a failure of understanding).
Any large sea inlet.
ETYM Old Eng. pit, put, as. pytt a pit, hole, Latin puteus a well, pit.
1. A concavity in a surface (especially an anatomical depression); SYN. fossa.
2. A sizeable hole (usually in the ground); SYN. cavity.
3. A trap in the form of a concealed hole; SYN. pitfall.
4. An open-surface excavation for extracting stone or slate; SYN. quarry, stone pit.
5. The stone-like seed at the core of certain fruits.
precipice / presəpəs /
ETYM French précipice, Latin praecipitium, from praeceps, -cipitis, headlong; prae before + caput, capitis, the head. Related to Pre-, and Chief.
1. A very steep or overhanging place, a very steep cliff.
2. A hazardous situation; broadly; brink.
profundity / prəfʌndɪti /
ETYM Latin profunditas: cf. French profondite. Related to Profound.
Intellectual depth; penetrating knowledge; keen insight; etc: SYN. profoundness.
steep / stiːp /
1. A steep place (as on a hill).
2. The state or process of being steeped
3. A bath or solution in which something is steeped
swallow hole / ˈswɑːloʊ hoʊl /
Or swallet; Hole, often found in limestone areas, through which a surface stream disappears underground. It will usually lead to an underground network of caves. Gaping Gill in North Yorkshire is an example.