Definition and background:
The lowest part in a musical composition. The lowest or deepest male voice usually of a range of F just below the bass clef to the E above middle C.See also basso cantante and basso profundo. The lowest pitched instrument in a family of instruments such as the bass recorder, double bass, bass clarinet, tuba, etc. the lowest of the standard four voice ranges (bass, tenor, alto, soprano); the lowest melodic line in a musical composition, often thought of as defining and supporting the harmony; in an orchestral context, the term usually refers to the double bass.(1) the lowest of the male voice types (2) the lowest of any family of instruments
1) The lower range of audio frequencies up to approximately 250 Hz. A reference value. 2) A freshwater fish that are caught in large numbers at various bass tournaments.
For more information on the music term "Bass" check out these other resources:
Wikipedia - Glossary of Musical Terminology
Virginia Tech Multimedia Music Dictionary
ORB -- Medieval Music Glossary