A person who wears a western (specifically Anglo-French)-style maid uniform. See wa maid for traditional Japanese maids.
In anime, maids typically wear some variation of the classic French or English maid uniform (the former is primarily decorative, with frills, short skirt, and bib apron, while the latter is usually an ankle-length or mid-calf length dark-colored dress with a pinafore apron). The most indicative sign that a woman is a maid is a white maid headdress and some sort of white maid apron.
If a character that is not usually portrayed with a maid uniform is drawn with one, also add the enmaided tag.