CORESPONDENT
corespondent, co-respondent
(noun) the codefendant charged with adultery with the estranged spouse in a divorce proceeding
Source: WordNet® 3.1
Etymology
Noun
corespondent (plural corespondents)
(legal) One of two or more persons against whom a lawsuit is made; but especially a person charged with committing adultery with the defendant in a divorce proceeding.
Source: Wiktionary
Co`-re*spond"ent (k`rr-spnd"ent), n. (Law)
Definition: One who is called upon to answer a summons or other proceeding
jointly with another.
Source: Webster’s Unabridged Dictionary 1913 Edition