Organized, large-scale, armed conflict between countries or between national, ethnic, or other sizeable groups, usually involving the engagement of military forces.

“The war was largely between Sunni and Shia militants.”

A particular conflict of this kind.

(by extension) Any conflict, or anything resembling a conflict.

“You look like you've been through the wars.”

To engage in conflict (may be followed by "with" to specify the foe).

To carry on, as a contest; to wage.