A prostitute is someone who engages in sexual acts for money. Prostitutes appear in all the Fallout games. Like virtually all other forms of illegal activity, prostitution flourished in the decline of law and order that followed the Great War.
Cherry and Fantasia at Dukov's Place ("party girls" who exchange sexual favors for Dukov's protection, unknown if they are actually prostitutes by profession).
Brianna, a member of The Family who offers her services to the male members.