1 [mass noun] resistance or dissent, expressed in action or argument:there was considerable opposition to the proposal
(often the opposition) a group of opponents, especially in sport, business, or politics:the home team made short work of the opposition
(the Opposition)British the principal parliamentary party opposed to that in office:the leader of the Opposition
Astronomy & Astrology the apparent position of two celestial objects that are directly opposite each other in the sky, especially the position of a planet when opposite the sun.
2a contrast or antithesis:a nature-culture opposition [mass noun]:the opposition between practical and poetic language
in opposition
in contrast or conflict:they found themselves in opposition to state policy
(of a major political party) not forming the government:the objectives of the party while in opposition