1) Low pitch indicator 2) Lower staff symbol 3) Notation on most piano music 4) Sheet music mark 5) Staff leader 6) Staff symbol 7) Symbol on a staff 
(from the article `clef`) The bass, or F, clef sets the position of the F below middle C. In modern notation this is fixed at the second line from the top of the staff:
The bass clef is also called an F clef because it shows the performer where the first F below Middle C is. If you were to draw horizontal lines from the main part of the clef out to the two dots, the bass clef would look a little like an F.
In music, a bass clef is the character placed at the beginning of the staff containing the bass part of a musical composition.
[n] - a clef that puts the F below middle C on the fourth line of a staff
symbol placed on the five-line staff in traditional notation indicating the pitch of the notes and locating F on the fourth line from the bottom.
F clef noun a clef that puts the F below middle C on the fourth line of a staff