Open English Wordnet
Nouns
(n)resistance, oppositionthe action of opposing something that you disapprove or disagree with“he encountered a general feeling of resistance from many citizens”, “despite opposition from the newspapers he went ahead”
(n)confrontation, oppositionthe act of hostile groups opposing each other“the government was not ready for a confrontation with the unions”, “the invaders encountered stiff opposition”
(n)enemy, foe, oppositionan armed adversary (especially a member of an opposing military force)“a soldier must be prepared to kill his enemies”