A hollow in the sand- or mud-banks on a shore. Also, a depression among sand-dunes.

local. See quots., and cf. sump, n.. Also, in Australia, a shallow lake or pond.

transferred. A natural formation suggesting a cauldron, in shape, or by the agitation of a contained fluid.

(a) a hollow or ditch in which pigs wallow; also in extended use; (b) (U.S.) a natural depression having a similar appearance; frequently attributive…

A deep depression or hole in the ground formed by erosion in limestone terrain.

transferred. A deep circular hollow scoured out in a rocky river bed, or under a glacier, etc.; a pot-hole. Cf. giant's kettle n. at giant, n. adj.com…

Chiefly U.S. A wide pit-like hollow in a canyon or fissure.

A depression or basin in a karstic limestone region, esp. one that is relatively extensive and funnel-shaped.

a depression in the ground thought to have been formed by the melting of an ice block trapped in glacial deposits, esp. one that is circular and…

a small low-lying area or hollow that is subject to frosts; = frost pocket n.

a crater or a hollow in the ground believed to have been produced by the impact of a meteorite.

A depression in the ground surface occurring in karstic regions (see quots.).

a small low-lying area or hollow that is subject to frosts; cf. pocket, n. 6c.

A doline, esp. one in the Causses region of France.

A broad conical or dome-shaped mound formed in regions with thin or discontinuous permafrost, consisting of a layer of soil over a large core of ice…

A natural ditch along the edge of a raised bog.

With plural agreement. Shallow rounded hollows in rock produced by weathering.