bat·tal·ion 
(b
ə-t
ăl
y
ən)
n.1. a. An army unit typically consisting of a headquarters and two or more companies, batteries, or similar subunits.
b. A large body of organized troops.
2. A great number: battalions of ants.
[French bataillon, from Old French, from Italian battaglione, augmentative of battaglia, from Vulgar Latin *battalia; see BATTLE.]