Per [[otoko_no_ko|trap]], a female character who looks and may or may not act masculine. Most likely also dresses like a male, although unlike mere [[crossdressing]] the character is assumed by others to be male until demonstrated otherwise.

As a rule of thumb, if you can correctly tell the gender with complete certainty from the thumbnail alone, it's not a reverse trap.

Often indicated on Pixiv by the [b]男装[/b] ([i]Dansou[/i] lit. "masculine clothes/disguising oneself as a man") and [b]男装の麗人[/b] ([i]Dansou no Reijin[/i] lit. "A beautiful woman disguised as a man") tags. See also [[tomboy]], which may overlap. pool #6118 may also overlap in some places, but is not necessarily the standard.
男装 男装の麗人 雄んなの子 伪郎 伪伪娘 正莉