To save this word, you'll need to log in.

: an opening in rock widened by natural forces (as weathering or solution)

especially : an opening in rock widened by natural forces (as weathering or solution)

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

More than 250,000 words that aren't in our free dictionary

Expanded definitions, etymologies, and usage notes

Advanced search features

Ad free!