Achillean, also known as men loving men (MLM), apollian, chaeronean, and chaeronic, refers to a man or man-aligned person who is attracted to other men or man-aligned people. One may or may not be attracted to other genders as well. This attraction does not need to be exclusive, as the label is used in a way to unify all men who love other men, including gay (vincian) men, bisexual men, pansexual men, etc, promoting solidarity among men of all identities.
The term is most commonly used as an umbrella term. It's typically used in combination with another identity to specify that one prioritizes their attraction to and relationships with other men. It is sometimes used as an identity on its own for people who know they are attracted to men but may be uncertain if they're attracted to other genders. The term can also be used to describe a relationship between two men.
The word achillean has historically been used to describe things relating to the mythological figure Achilles. The first instance of achillean being used in the context of men attracted to men is likely a 2016 post by Tumblr user Asculan.
The achillean flag has two blue stripes on the top and bottom representing men. In the center is a green carnation. In ancient Rome and 19th century England green indicated gay affiliations. Victorian men would often pin a green carnation on their lapel as popularized by author Oscar Wilde.
An alternative flag uses a darker blue with a green stripe alongside the green carnation, with the same symbolism.
The original achillean flag had the same two blue stripes on the top and bottom representing men as the current flag. In the center was a realistic green carnation, but this flag was too complicated for many and could not easily be made in vector formats, leading to the creation of the current flag.
The word achillean comes from the name of the hero in the Iliad, Achilles, who was romantically involved with another man, Patroclus.