The Collaborative International Dictionary of English v.0.48:

F \F\ ([e^]f).
   1. F is the sixth letter of the English alphabet, and a
      nonvocal consonant. Its form and sound are from the Latin.
      The Latin borrowed the form from the Greek digamma ?,
      which probably had the value of English w consonant. The
      form and value of Greek letter came from the Ph[oe]nician,
      the ultimate source being probably Egyptian.
      Etymologically f is most closely related to p, k, v, and
      b; as in E. five, Gr. pe`nte; E. wolf, L. lupus, Gr.
      ly`kos; E. fox, vixen; fragile, break; fruit, brook, v.
      t.; E. bear, L. ferre. See Guide to Pronunciation,
      [sect][sect] 178, 179, 188, 198, 230.
      [1913 Webster]

   2. (Mus.) The name of the fourth tone of the model scale, or
      scale of C. F sharp (F [sharp]) is a tone intermediate
      between F and G.
      [1913 Webster]

   F clef, the bass clef. See under Clef.
      [1913 Webster]

WordNet (r) 3.0 (2006):

F clef
    n 1: a clef that puts the F below middle C on the fourth line of
         a staff [syn: bass clef, F clef]