Noun

opponent (plural opponents)

1. An individual or group who is a rival of another.
2. One who attempts to stop the progression of.
3. One who objects to.
4. In team sports, a player of an opposite team.

Antonyms

• supporter
• proponent
• advocate

Adversary

Adversary may refer to:

In Judeo-Christian religion:

• Satan, whose name means "adversary" in Hebrew.

In computer science:

• Adversary (cryptography) is a malicious entity in cryptography whose aim is to prevent the users of the cryptosystem from achieving their goal.
• Adversary (online algorithm), the adversary model is used in online algorithms in order to show competitiveness of randomized algorithms.

In fiction:

• Adversary (comics), villain from the Marvel comics universe
• Geppetto (Fables), a character from the comic book series Fables also known as "The Adversary"
• "The Adversary" (DS9 episode), the season finale of Star Trek: Deep Space Nine's third season
• The Adversary, book four in "The Saga of the Exiles" by Julian May

In Dance:

• Ad·ver·sary, Canadian industrial dancer.
• The Adversary (album), solo album by Ihsahn of the Norwegian black metal band Emperor

In law:

• Adversarial system, a system of law commonly used in common-law countries
• Adversary proceeding, proceeding used in bankruptcy processes