n. 1 a the brother of one's father or mother. b an aunt's husband. 2 colloq. a name given by children to a male family friend. 3 sl. esp. hist. a pawnbroker. Uncle Sam colloq. the federal government or citizens of the US (will fight for Uncle Sam). Uncle Tom derog. a Black man considered to be servile, cringing, etc. (from the hero of H. B. Stowe's Uncle Tom's Cabin, 1852).
[ ME f. AF uncle, OF oncle f. LL aunculus f. L avunculus maternal uncle: see AVUNCULAR ]