Yes, trap is a term they (and other groups) use for transgender people (and especially trans women), since, as many people see it, 1)we are still men and 2)we make ourselves look like women to trap them in to having sex with men and thus further destroy their masculinity.
So in order for a trans female to be a "trap" they'd have to actually pass as female.
Well... i suppose it would be easier if they'd just tell the other person that they were born male/biologically male. I mean no one likes finding this sort of thing in the last possible moment ^_^