sesquialtera

from The Collaborative International Dictionary of English v.0.48

Sesquialter \Ses`qui*al"ter\, Sesquialtera \Ses`qui*al"ter*a\,
   n. [NL. sesquialtera.] (Mus.)
   A stop on the organ, containing several ranks of pipes which
   reenforce some of the high harmonics of the ground tone, and
   make the sound more brilliant.
   [1913 Webster] Sesquialteral