Definition of a reverse trap I am confused at how people describe gender roles and their trope classification in anime. I understand that traps are characters appearing to be girls but are actually guys. One of my favorite traps of all time is Steins;Gate's Ruka Urushibara. 

However, I don't get what "reverse traps" are. Are they appearing to be traps but are actually legit girls (a trap trap)? Or a character that initially appears to be a boy, but is actually a girl (a girl trap)? For clarity, consider what you would call Charlotte (Charles) Dunios from Infinite Stratos.

 

EDIT: This post is not intended to be offensive to other genders in any way, the naming convention of "traps" pertain to fictional characters in anime/manga only.
A traditional 'trap' is a boy disguised as a female. Note that this is not simply boys who look feminine, but characters who are pretending to be the opposite sex or who are presumed to be by the narrative of the medium. 

Example 'traditional' trap:

Maria from Maria✝Holic



&amp; Steins;Gate's Ruka Urushibara (as you mentioned earlier)

Not a trap: Ryuunosuke Akasaka (The Pet Girl of Sakurasou)



A 'reverse trap' is simply the opposite - A female character pretending to be a male one. This is why Charlotte falls under this category. (Until she is outed to be a female). Similar to above, characters who are masculine are not strictly reverse traps.

Example 'reverse' trap:

Haruhi Fujioka - Ouran Highschool Host Club



Not a reverse trap: Yū Kashima from Nozaki-Kun