'Sackbut' definitions:

Definition of 'sackbut'

noun

A medieval musical instrument resembling a trombone

From: GCIDE

Sackbut \Sack"but\, n. [F. saquebute, OF. saqueboute a sackbut, earlier, a sort of hook attached to the end of a lance used by foot soldiers to unhorse cavalrymen; prop. meaning, pull and push; fr. saquier, sachier, to pull, draw (perhaps originally, to put into a bag or take out from a bag; see Sack a bag) + bouter to push (see Butt to thrust). The name was given to the musical instrument from its being lengthened and shortened.] (Mus.) A brass wind instrument, like a bass trumpet, so contrived that it can be lengthened or shortened according to the tone required; -- said to be the same as the trombone. [Written also sagbut.] --Moore (Encyc. of Music). [1913 Webster]
Note: The sackbut of the Scriptures is supposed to have been a stringed instrument. [1913 Webster]

Sackbut (Chald. sabkha; Gr. sambuke), a Syrian stringed instrument resembling a harp (Dan. 3:5, 7, 10, 15); not the modern sackbut, which is a wind instrument.