crumb /kɹʌm/noun 8verb 2forms 3phrases 2 noun8 •A small piece which breaks off from baked food (such as cake, biscuit or bread).The pigeons were happily pecking at crumbs of bread on the ground. •A small piece of any other solid substance.Then erase any pencil lines with a good, soft eraser, rubbing gently, in only one direction. A dustbrush can be useful in removing any eraser crumbs. — 2012 •(figurative) A bit, small amount. •Ellipsis of crumb rubber.Production of rubber granules, or crumb, is well-established in this country. — 2007 •The soft internal portion of bread, surrounded by crust.Dust unto dust, what must be, must; / If you can't get crumb, you'd best eat crust. — 1861 •(slang) A nobody; a worthless person.All Dad can think of is a gift certificate from the Melody Inn? And my crumb of a boyfriend doesn't even show up? This is a birthday? — 1999 •A mixture of sugar, cocoa and milk, used to make industrial chocolate. •(slang) A body louse (Pediculus humanus). verb2 •To break into crumbs or small pieces with the fingers; to crumble. •To cover with crumbs. formscrumbed · crumbing · crumbs Phrases with crumb crumb downto clean by removing crumbs from crumb upTo mess up (something); to make (something) dirty.