Mustang (military officer)

Mustang is a military slang term used in the United States Armed Forces to refer to a commissioned officer who began their career as an enlisted service member. A mustang officer is not a temporary or brevet promotion but is a commissioned officer who receives more pay according to their rank of O1-E, O2-E, etc., but has no more command responsibilities than those of any commissioned officer of the same grade.

Source: Wikipedia — Mustang (military officer) (CC BY-SA 4.0)