The Collaborative International Dictionary
Sesquialter
Sesquialter \Ses`qui*al"ter\, a. Sesquialteral.
Sesquialter
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 re["e]nforce some of the high harmonics of the ground tone, and make the sound more brilliant.
Wiktionary
sesquialter
a. (alternative form of sesquialteral English)