The term used for the person against whom an appeal of a court decision is brought or a term for the person answering a complaint in a civil case.
Merriam-Webster Online Dictionary
respondent (noun)1.
one who as - responds
a) one who maintains a thesis in reply
b) (1) one who answers in various legal proceedings (as in equity cases)
(2) the prevailing party in the lower court
c) a person who responds to a poll
2.
a reflex that occurs in to a specific external stimulus - response compare operant
1.
making - response responsive , especially being a respondent at law
2.
relating to or being behavior or to a stimulus that are followed by a reward - responses respondent conditioning compare operant 3