From The Collaborative International Dictionary of English v.0.48:
Howitzer \How"itz*er\, n. [G. haubitze, formerly hauffnitz,
Bohem. haufnice, orig., a sling.] (Mil.)
(a) A gun so short that the projectile, which was hollow,
could be put in its place by hand; a kind of mortar.
[Obs.]
(b) A short, light, largebore cannon, usually having a
chamber of smaller diameter than the rest of the bore,
and intended to throw large projectiles with
comparatively small charges.
[1913 Webster]