A combination of both a mouth and anus in one.
A sea anemone eats and defecates with its manus.
Manus may also refer to the mouth of someone who only talks shit.
Peter - "My anemone looks better today, hss opened up, you can see his manus now."
Joni - "Haha his white rimmed manus"
Peter - "Your mate should just keep his manus closed."