This character is a girl who looks like, and is usually mistaken, for a boy.
Dressing and acting like a boy is optional.
"Trap" does not imply any specific form of sexual orientation but only the physical appearance.
This trait is to be used for works that explicitly frame a female character as male in order to "trap" the player. For gender ambiguous body types use Androgynous instead. For characters whose self-described gender identity does not match their sex, use Transgender.
Do not apply the trait to transsexual characters, as it is a separate fetish. A possible exception could be allowed, if the character starts as a Reverse-trap and later transitions during the course of the story.