1. Cotton or flannel plad drawstring or elastic waistband pants that men wear to bed or when just chilling around the house. Usually they have an opening in the front with a single button or a drawstring.
2. If a man sleeps naked, this is sometimes referred to as wearing manjamas.
3. If you tell your young son to go put his pajamas on, to make him feel more like a big boy you might call them manjamas.
Look honey, I'm wearing my manjamas.
Son, go put your manjamas on and then I'll read you a story.