Webster's Revised Unabridged Dictionary · 1913

Sesquialter

Sesquialter , adjective

Sesquialteral.

Sesquialter , noun

[New Latin sesquialtera.]

(Music) 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.

Also: Sesquialtera