crumble

Short definition from Wiktionary

Verb

1. 1
   To fall apart; to disintegrate.
2. 2
   To break into crumbs.
3. 3
   To mix (ingredients such as flour and butter) in such a way as to form crumbs.

Noun

1. 1
   A dessert of British origin containing stewed fruit topped with a crumbly mixture of fat, flour, and sugar.

Proper noun

1. 1
   A surname.