The Collaborative International Dictionary of English v.0.48:

Harquebus \Har"que*bus\ Harquebuse \Har"que*buse\
   (h[aum]r"kw[-e]*b[u^]s), n. [See Arquebus.]
   A firearm with match holder, trigger, and tumbler, made in
   the second half of the 15th century. The barrel was about
   forty inches long. A form of the harquebus was subsequently
   called arquebus with matchlock.
   [1913 Webster]

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):

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