crumble C1

/ˈkɹʌmbəl/ To break or fall apart into small pieces.

crumb C1

/kɹʌm/ A tiny piece that breaks off bread, cake, or similar food.

crummy C2+

/ˈkrʌmi/ of poor quality; shabby or unpleasant

crumblet C2+

/ˈkrʌmblət/ a small crumb or fragment