A Hostility

1. (uncountable) The state of being hostile.

2. (countable) A hostile action, especially a military action. See hostilities for specific plural definition.

(state of being hostile): antagonism, opposition, enmity, animosity, antipathy, hatred, unfriendliness

(military action): war, fighting, combat

(state of being hostile): amity, friendliness

(military action): peace