Within the Transgender and BDSM community, where one male partner adopts the persona of a female's traditional role, in the sexual activity of the two. This is in a more pronounced manner, than just being the submissive partner.
In traditional man on man relationships, one is classed as a bottom or a top, but in a Sissie (transgender) context, the submissive goes beyond just being a bottom.
This involves adopting mannerisms, associated with women, in a traditional sense.
It includes dressing as a woman, as well as adopting other feminine persona traits.
This includes mannerisms, gestures, including talking, how one sits, etc.
Being 'Sissified' is a voluntary decision by the submissive male, though in some dominant scenarios, it could be considered 'forced' as a requirement by the more dominant male.
Practice (Associated Acts):
Extreme scenarios include the changing of names, to those more feminine sounding.
Usually it includes transforming the male name, to a feminine version, usually which has an [a] and [i] sounding added to the end.
Stephen would become Stephanie, Joseph turns into Josephine and so on.
There are some exceptions, such as Samuel would become or change to Samantha.
While this can lead to further changes, including physically altering one's body, it can also simply exist in a manner of role playing, within a BDSM context.
This would include the dressing up in outfits, such as a Maid, or Nurse, or other traditional feminine roles, to act out a scene, during sexual activity.