muswe (or musve)
from a slang perspective, this means a person (or a bottom) who likes to take on a receptive role (kufemerwa mugotsi) and in a BDSM context, this refers to whoever plays a passive, or submissive role within the relationship.
nyanga
this is what you'd call a "top" id est, a person who prefers to be more masculine and dominant and therefore takes on the penetrative role (kufemera mugotsi) by controlling the whole situation.