Sissification refers generally to the feminization of a male, more specifically, without their will or without their knowledge. The term was originally used in the context of BDSM to refer to a male submissive that underwent forced feminization or gender reassignment, but also refers to the loss of hyper-masculinity in society.
More About Sissification
Sissification in a BDSM context refers to a male submissive that is effeminate or exhibits feminine behaviors. This is typically done at the request of the dominant. The submissive is “forced” into cross-dressing and gender reassignment. Generally, a sissy refers to a man that does not conform to traditional gender roles. Sissy is thought of as the male equivalent of tomboy although this term is thought of as being more offensive.