A professional switch or pro-switch is a professional switch, i.e. a person who is comfortable with both dominant and submissive roles in BDSM play, and offers both of these services for money. As such, a pro-switch (usually female) is a pro-domme and a pro-sub rolled into one.
Some pro-switches use a single name/pseudonym, while others use different names/pseudonyms for their dominant or submissive side, such as (fictive example) "Mistress Alpha" for her role as a dominatrix and "slavegirl beta" for her role as a submissive. The clients may or may not be aware of the woman's "other side".