'biff' definitions:

Definition of 'biff'

(from WordNet)
noun
(boxing) a blow with the fist; "I gave him a clout on his nose" [syn: punch, clout, poke, lick, biff, slug]
verb
Strike, usually with the fist; "The pedestrians pummeled the demonstrators" [syn: pummel, pommel, biff]

Synonyms of 'biff'

From: Moby Thesaurus