A male character who looks or acts feminine, often passing as female.
The Japanese term "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).
Otoko no ko characters are sometimes called "traps" or "femboys" in English-speaking communities. These terms have been deprecated in some areas (including this site, which aliases both tag names to this one) due to use as anti-LGBT slurs.
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.
