/euh gresh"euhn/ , n.
1. the action of a state in violating by force the rights of another state, particularly its territorial rights; an unprovoked offensive, attack, invasion, or the like: The army is prepared to stop any foreign aggression.
2. any offensive action, attack, or procedure; an inroad or encroachment: an aggression upon one's rights.
3. the practice of making assaults or attacks; offensive action in general.
4. Psychiatry. overt or suppressed hostility, either innate or resulting from continued frustration and directed outward or against oneself.
[ 1605-15; aggression- (s. of aggressio ), equiv. to aggress ( us ) (see AGGRESS) + -ion- -ION ]
Ant. 1. peacefulness.