A very disrespectful word used specifically against transfemme (and sometimes masc) community, meaning "a man or woman" who deceived you and made you believe that they were a different gender and "tricked you into sleeping with them".
"Did you see Stephie? Michael said he's a trap."
"I think you mean she, douchebag. And fuck off, dickface."
A male who does not identify as female but tries to resemble one as closely as possible, is also usually more attractive than other women and when you try to have sex with them, you fall for the inevitable "trap" and fuck a dude.