A male character who looks or acts feminine, often passing as female.
The Japanese term 男の娘 (otoko no ko) is a pun on 男の子 (otoko no ko), meaning "boy", replacing 子 with the ko reading of 娘 (commonly musume, girl).
Across English-speaking communities, these characters are referred to in a number of different ways with no single standard term. The most common are "trap" and "femboy", and less frequently "tomgirl" or "otokonoko" are used.
Some communities have mistakenly taken to using the term as a word for feminine boys no matter if they convincingly look like girls or not. If you can correctly tell the character is male with complete certainty from the thumbnail alone without looking at the genitalia, it's not this.
While many otoko no ko engage in crossdressing, it is not a requirement. Sufficiently feminine characters can pass as girls even when near-nude or dressed in typically masculine clothing.
