Domme
From wipipedia.org
The noun Domme is pseudo-French female variation of the term Dom, which is a shortened version of the word dominant.
Someone who sometimes like to be Domme and sometimes likes to be a sub is called a Switch.
There is confusion on its pronunciation, with some pronouncing it identically to dom and some pronouncing the final e as a second syllable, e.g. saying dom-MAY or DOM-may. Many prefer the first pronunciation (identical to dom), by analogy to one-syllable French-derived words like femme or blonde.
See the gender-neutral term Dom for information on the role of Domme.