The Collaborative International Dictionary of English v.0.48:

Shrill \Shrill\, a. [Compar. Shriller; superl. Shrillest.]
   [OE. shril, schril; akin to LG. schrell, G. schrill. See
   Shrill,v. i.]
   Acute; sharp; piercing; having or emitting a sharp, piercing
   tone or sound; -- said of a sound, or of that which produces
   a sound.
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         Hear the shrill whistle which doth order give
         To sounds confused.                      --Shak.
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         Let winds be shrill, let waves roll high. --Byron.
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