Femme is a term used in LGBT+ subculture to describe someone, typically a lesbian or otherwise sapphic woman, who has a feminine gender presentation. The term can refer to any LGBT+ femininity, but often refers to overblown and/or outwardly atypical femininity.
Femmes will often dress in feminine clothing, and typically present themselves in a more stereotypically feminine way, such as having long hair and wearing makeup. Femmes are also commonly thought of as having more "feminine" interests. However, femmes often subvert cultural expectations of femininity or show femininity in a uniquely LGBT+ way, as opposed to cishets. Some transmasculine femmes may not take certain steps associated with transmasculine transition, such as going on testosterone. Femmes can be cisgender, transgender, or any other gender modality. Femme can also be used by non-binary people.
Femme men often use the spelling "fem," which is simply the older version of "femme" and was also used by LGBT+ women before "femme" became common. When said out loud, the terms sound identical. Femme men are associated with highly exaggerated feminine style and manner, which is often a reclamation of the derogatory association of SGA men with femininity. Some femme men enjoy drag, and other have a more subdued but clearly feminine style. The infamous "gay accent" is associated with, but not always used by, these men.
Traditionally, femmes have been expected to be attracted to butches. For some femmes, this attraction to butches represents a strong part of their own identity. However, some femmes are attracted to other femmes. This is sometimes referred to as "fem-for-fem" or "femme-for-femme."
Some other terms that are typically synonymous with femme include "lipstick lesbian" and "designer dyke."
Someone who is highly feminine, typically putting in a lot of effort into their appearance. They may also choose to only date butches.
High femme is also sometimes defined as a femme who likes receive sexual contact but doesn't want to reciprocate, the opposite of stone. Sometimes this can carry a negative connotation, but they often form a sexual dynamic with a stone butch. (They may also identify as asexual and/or iamvanosexual.)
Stone femme may refer to a femme who is stone, meaning they do not like their genitals sexually touched by their partners. (They may also identify as asexual and/or placiosexual.) It may also refer to the femme partner of a stone butch.
Blue Jeans Femme
Someone who is femme but prefers more casual clothes.
Flag and Symbols
The femme flag was designed by Tumblr user noodle on or before Feb 9th, 2018. Purple was chosen based on one of the colors from the orange/pink lesbian flag.
The purple/pink femme lesbian flag was designed by an unknown person on or before September 30, 2019.
An alternate femme lesbian flag was designed by Reddit user u/ShippyGoodness on August 9, 2020.
Another alternate femme lesbian flag was designed by wiki user Wemrotung on March 28, 2021.
The inclusive femme flag was designed by Tumblr user nbgender on January 14, 2021.
Twitter user strwbryfemme created another femme lesbian flag on April 2, 2021. The color chosen for the flag was hot pink and the design was made to match the well-known orange butch lesbian flag. 
The femme symbol was designed on October 4, 2014 by a group of non-binary Brazilians. It is based on the female symbol but with longer prongs.