Otome are elite female warriors, employed by important political figures as bodyguards. Their
powers and skills are vast making them by definition supersoldiers (in a unorthodox fashion as they are also technically magical girls), as Nao explains to Arika the military strength of any country is measured by the number and quality of its Otome. On the planet Earl, where the series takes place, only one place exists where
Otome receive their powers from nanomachines injected into their blood which granted peak-human strength and limited healing abilities. However, said nanomachines are vulnerable to the prostate specific antigen (PSA); acting as an antigen, PSA causes an Otome's body to develop immunity against nanomachines (and any future injections), rendering her permanently powerless. Therefore, Otome cannot engage in sexual intercourse with males.
This is, however, not the way it is spelled in the original title of Mai-Otome (舞-乙HiME Mai-Otome?), which only uses the first kanji of the word. In written form, Otome are called 乙HiME (乙-type Highly-advanced Materialising Equipment).
A Meister (pronounced "MaiStar") Otome is an Otome who is a qualified graduate. This is proven through the design of the GEM, which is different than that of the students'. In English, meister brings about the meaning 'a person who is good in what he/she does'. Therefore, it can be said that a Meister Otome is an elite Otome. However, Meister also means "Master" in German. Meister Otome also receive a title based on their GEM that can be inherited by passing on the GEM, for instance Lena Sayers and Arika Yumemiya are both referred to as the Blue Sky Sapphire.