A social gathering especially for pleasure or amusement: a cocktail party. A group of people who have gathered to participate in an activity. See Synonyms at band2. An established political group organized to promote and support its principles and candidates for public office. A person or group involved in an enterprise; a participant or an accessory: I refuse to be a party to your silly scheme. Law A person or group involved in a legal proceeding as a litigant. A subscriber to a telephone party line. A person using a telephone. A person: "And though Grainger was a spry old party, such steps couldn't be his\u201d ( Anthony Hyde). A selected group of soldiers: a raiding party. Slang An act of sexual intercourse. Slang An orgy. Of, relating to, or participating in an established political organization: party members; party politics. Suitable for use at a social gathering: party dresses; a party hat. Characteristic of a pleasurable social gathering: a party atmosphere. To celebrate or carouse at or as if at a party: That night we partied until dawn.