Emily Dickinson Lexicon

SACK'BUT, n. [Sp. sacabuche; the tube or pipe of a pump, and a sackbut; Port. sacabuxa or saquebuxo; Fr. saquebute. The Dutch call it schuif-trompet, the shove-trumpet, the trumpet that may be drawn out or shortened. Sack then is of the same family as the preceding word, signifying to pull or draw. The last syllable is the L. buxus.]

A wind instrument of music; a kind of trumpet, so contrived that it can be lengthened or shortened according to the tone required. – Encyc.