one who accompanies or is in company with another for a longer or shorter period, either from choice or casually; one who is much in the company of, or is associated with, another or others; an associate; a comrade; a consort; a partner.-a knight of the lowest rank in certain orders; as, a companion of the bath.-a fellow; -- in contempt.-a skylight on an upper deck with frames and sashes of various shapes, to admit light to a cabin or lower deck.-a wooden hood or penthouse covering the companion way; a companion hatch.-to be a companion to; to attend on; to accompany.-to qualify as a companion; to make equal.