1.to strike, smite: to strike one against another, κρ. χεῖρας to clap hands, Eur.; κρ. τὰ ὅπλα πρὸς ἄλληλα Thuc., etc.:— κρ. τὸν πόδα (i. e. κρ. τὴν γῆν τῶι ποδί) in dancing, Eur.
2.κέραμον κρούειν to tap an earthen vessel, to try whether it rings sound: hence to examine, prove, Plat.
3.to strike a lyre with the plectron, id=Plat.
5.as a nautical term, in Mid., κρούεσθαι πρύμναν, like ἀνακρούεσθαι, to back a ship, Thuc.