Pyjamas \Py*ja"mas\, or, chiefly U. S., Pajamas \Pa*ja"mas\, n. pl. A garment, similar to the Oriental pyjama (which see), adopted among Europeans, Americans, and other Occidentals, for wear in the dressing room and during sleep; also, a suit of drawers and blouse for such wear.

Source: Webster's Revised Unabridged Dictionary (1913)