The Collaborative International Dictionary of English v.0.48:

Arquebus \Ar"que*bus\, Arquebuse \Ar"que*buse\ (?; 277), n. [F.
   arquebuse, OF. harquebuse, fr. D. haak-bus; cf. G.
   hakenb["u]chse a gun with a hook. See Hagbut.]
   A sort of hand gun or firearm; a contrivance answering to a
   trigger, by which the burning match was applied. The musket
   was a later invention. [Written also harquebus.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

arquebus
    n 1: an obsolete firearm with a long barrel [syn: arquebus,
         harquebus, hackbut, hagbut]