A region where a battle is being (or has been) fought(noun)
WordNet. Princeton University. 2010.
Use "field of battle" in a sentence
"On the field of battle one object of regret cannot long engross the mind; yet, on his return to Cairo, Bonaparte frequently spoke to me of Sulkowsky in terms of unfeigned sorrow."
"And most important of all, what did the alien want, now that it had left the field of battle and come, in all its might and otherworldly magnificence, to Metrel?"
"They were crowding him out, these irresistibly subtle deep probers, shoving the mere proprietor of the mental field of battle aside."