Forced feminisation
From wipipedia.org

Forced feminisation is the process of forcing a man to be like a woman, generally as a means of humiliation or of asserting that the man is the bottom in a BDSM relationship.
This can take various forms:
- Force him to wear female clothes (cross-dressing), possibly in a way that makes him look ridiculous; very feminine clothes such as stockings, frilly knickers, petticoats and stilettos, or revealing ones such as miniskirts, may be used.
- Include a wig, false breasts, make-up, etc. in an attempt to make him a passable female.
- Make him behave in an effeminate manner, or train him (for example, by deportment classes) to act like a female.
- Force him into a submissive role characteristic of stereotype females, for example that of a maid.
- Dress him and make him behave like a young child; this is a form of age play.
- Make him take part in sexual acts, with a female or another male, in a role more typical of females.
- Force him to have gender reassignment therapy, medical or even surgical.
Associated activities may include forced exhibitionism, spanking and tightlacing in a corset.