Volume 3: 1771 Edition of the Encyclopedia Britannica!
Sackbut
Sackbut, a musical instrument of the wind kind, being a sort of trumpet, though different from the common trumpet both in form and size: it is fit to play a bass, and is contrived to be drawn out or shortened, according to the tone required, whether grave or acute. The Italians call it trombone, and the Latins tuba ductilis.