ri·fle 1 
(rīfəl)
(rīfəl)n.
1.
a. A firearm with a spirally grooved bore, designed to be fired from the shoulder.
b. An artillery piece or naval gun with a spirally grooved bore.
2. rifles Troops armed with rifles.
tr.v. ri·fled, ri·fling, ri·fles
To cut spiral grooves within (a gun barrel, for example).
[Short for rifle gun, rifled gun, from rifle, to cut spiral grooves in, from French rifler, to scratch, from Middle French, from Old French; see RIFLE2.]