General Meanings:

If you dream that you faced an adversary so it symbolizes that you will protect yourself and the others from any harm. In the dream you overcame the adversary it signifies that you will avoid any difficulties you will deal with everything. Do not worry, because you will make order.

Traditional Meanings:

European (Judeo-Christian)

• Be ready if meet adversity – To meet adversary in the dream so this dream is a warning that you may be immediately attacked by enemies, you should defend your own interests;
• Illness if adversary – The adversity in the dream may announce upcoming disease so you have to be attentive;
• No disaster if defeated adversary – The dream where you overwhelmed your adversary or adversaries, then this means that you will escape from the consequences of a disaster.

M. Ibn Sirin dreambook:

Adversary is qualified as an opponent by Muslim interpreter of dreams M. Ibn Sirin
Islamic dream meanings and interpretations about an opponent by Muhammad Ibn Sirin

Opponent  meaning in Islam:
(same meanings for dreams about adverse, contrast or opposite)

• If the dreamer’s opponent is a dead person in the dream, then the happiness and the good luck will come in life.
• If the opponent is alive, then the better luck will come to that dreamed person.

* Please, also read dream meaning of enemy.