IPA: //fɔːrˈwɔːrn//
KK: /fɔrˈwɔrn/
To give someone a warning about something that might happen in the future.
I want to forewarn you about the heavy traffic tomorrow.
Past: forewarned
Past Participle: forewarned
Forewarn → It is formed from "fore-" (meaning before) and "warn" (from Old English "warnian", meaning to give notice or to advise). The word "forewarn" means to give notice or advice before an event occurs.
Think of being told something 'before' ('fore-') it happens — that's what forewarn means.