Crumble

1. v. i. To fall into small pieces; to break or part into small fragments; hence, to fall to decay or ruin; to become disintegrated; to perish.
2. v. t. To break into small pieces; to cause to fall in pieces.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.