(astronomy) The apparent relative position of two celestial bodies when one is at an angle of 180 degrees from the other as seen from the Earth.
The action of opposing or of being in conflict.
An opposite or contrasting position.
An opponent in some form of competition.
(politics) A political party opposed to the party or government in power.
(law) In United States intellectual property law, a proceeding in which an interested party seeks to prevent the registration of a trademark or patent.