treb·le 
(trĕbəl)
(trĕbəl)adj.
1. Triple: "treble reason for loving as well as working while it is day" (George Eliot).
2. Music Relating to or having the highest part, voice, or range.
3. High-pitched; shrill.
n.
1. Music
a. The highest part, voice, instrument, or range.
b. A singer or player that performs this part.
2. A high, shrill sound or voice.
tr. & intr.v. treb·led, treb·ling, treb·les
To make or become triple.
[Middle English, from Old French, from Medieval Latin triplum, from Latin, neuter of triplus, triple; see TRIPLE.]
treble·ness n.
trebly (trĕblē) adv.