Definition of infantries:
(n) :
Soldiers who fight on foot (on land), as opposed to cavalry and other mounted units, regardless of external transport (e.g. airborne).
(n) :
(uncountable) The part of an army consisting of infantry soldiers, especially opposed to mounted and technical troops.
(n) :
A regiment of infantry.
(n) :
(colloquial, humorous) Infants; children.