Virescin is a term for all gay men, gay man-aligned people, and non-aligned people who are gay for men, meaning men-loving men and non-binary-loving-men. It can be a stand-alone identity, but it also brings together all people who are gay for men.
The general consensus is that the term is no longer in use.
Virescin comes from the word virescent, meaning greenish. It is based off green carnations, a symbol associated with gay men in the late Victorian and early Edwardian eras in England and with Oscar Wilde in particular. 
Virescin was created on a Discord server that hosted the former mods of the virescin Tumblr account on November 29, 2017. On December 1, 2017, one of the mods requested that people stop using the term. The original post was deleted, and the blog was abandoned.
The original virescin flag was created on November 29, 2017 by the virescin Tumblr account. The flag was made of five horizontal stripes of equal thickness. From top to bottom, the colors of the stripes were dark green, green, yellow-green, yellow, and purple. The shades of green represented energy, strength, sexuality, and life. The shades of yellow represented unity and happiness. The use of purple was meant to represent loyalty and love, specifically love for men.
An alternate flag was created by FANDOM user RoseWatera on November 18th 2020. It has no confirmed meaning.