adversary

[ad-ver-ser-ee]

noun, plural ad·ver·sar·ies.

a person, group, or force that opposes or attacks; opponent; enemy; foe.
a person, group, etc., that is an opponent in a contest; contestant.
the Adversary, the devil; Satan.

adjective Also especially British, ad·ver·sar·i·al [ad-ver-sair-ee-uhl] /ˌæd vərˈsɛər i əl/.

of or relating to an adversary.
involving adversaries, as plaintiff and defendant in a legal proceeding: an adversary trial.

Origin of adversary

1300–50; Middle English adversarie < Latin adversārius, equivalent to advers(us) (see adverse) + -ārius -ary; replacing Middle English adversere < Anglo-French
Related formsad·ver·sar·i·ness, nounnon·ad·ver·sar·i·al, adjective

Synonym study

1. Adversary, antagonist mean a person or a group contending against another. Adversary suggests an enemy who fights determinedly, continuously, and relentlessly: a formidable adversary. Antagonist suggests one who, in hostile spirit, opposes another, often in a particular contest or struggle: a duel with an antagonist.

Antonyms for adversary

1. ally.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for adversarial

adversarial

adjective

pertaining to or characterized by antagonism and conflict
British having or involving opposing parties or interests in a legal contestUS term: adversary

adversary

noun plural -saries

a person or group that is hostile to someone; enemy
an opposing contestant in a game or sport

adjective

the US term for adversarial (def. 2)

Word Origin for adversary

C14: from Latin adversārius, from adversus against. See adverse
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for adversarial
adj.

by 1892, from adversary + -al (1). Probably coined to avoid confusion which might arise with use of adversary (adj.), which is attested from late 14c. Related: Adversarially.

adversary

n.

mid-14c., aduersere, from Anglo-French adverser (13c.), Old French adversaire "adversary, opponent, enemy," or directly from Latin adversarius "opponent, adversary, rival," noun use of adjective meaning "opposite, hostile, contrary," literally "turned toward one," from adversus "turned against" (see adverse). The Latin word is glossed in Old English by wiðerbroca.

Online Etymology Dictionary, © 2010 Douglas Harper