in ‧ for ‧ mant /ɪnˈfɔːmənt $ -ɔːr-/ BrE AmE noun [countable]
[ Word Family: noun : ↑ informant , ↑ information , ↑ informer , ↑ misinformation , ↑ disinformation ; verb : ↑ inform , ↑ misinform ; adjective : ↑ informative ≠ UNINFORMATIVE , ↑ informed ≠ ↑ uninformed ; adverb : ↑ informatively ]
1 . someone who secretly gives the police, the army etc information about someone else SYN informer :
One of the witnesses was a paid informant for the FBI.
2 . technical someone who gives information about their language, social customs etc to someone who is studying them