a small fragment of bread, cake, biscuit, or cheese

a small amount

a crumb of comfort

the soft inner part of a loaf of bread, as distinct from the outer crust

loose crumbly soil

NAmer, informal a contemptuous term for somebody one despises

to cover or thicken (food) with crumbs

to break up (food or some other substance) into crumbs

Add the crumbed biscuits to the melted mixture