لُجْحٌ

A thing in the lower part of a well, and of a valley, like what is called a دَحْل: (S, K:) or, in the lower part of a well, and of a mountain, like a نَقْب: (L:) originally لُحْجٌ, from which it is formed by transposition: (T:) plural أَلْجَاحٌ. (L.)