Definition from Wiktionary, the free dictionary
From Old English cruma (“crumb, fragment”). The b appeared in the mid 15th century to match crumble and words like dumb, numb, thumb.
crumb (plural crumbs)
- A small piece which breaks off from baked food (such as cake, biscuit or bread).
- The pigeons were quite happily picking at bread crumbs on the ground.
- (figuratively) A bit, small amount.
- a crumb of comfort
- The soft internal portion of bread, surrounded by crust.
- A mixture of sugar, cocoa and milk, used to make industrial chocolate.
- (slang) A nobody, worthless person.
- (slang) A body louse.
Derived terms 
Related terms 
small piece of biscuit, cake, etc
(figurative) small amount
soft internal portion of bread
- The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.
Translations to be checked
- To cover with crumbs.
- To break into crumbs or small pieces with the fingers; to crumble.
- to crumb bread