Bass1  —n. 1 a lowest adult male singing voice. B singer with this voice. 2 instrument pitched lowest in its family. 3 colloq. Bass guitar or double-bass. 4 low-frequency output of a radio, record-player, etc. —adj. 1 lowest in musical pitch. 2 deep-sounding.  bassist n. (in sense 3). [from *base2 altered after italian basso]