any closefitting head covering, brimless or with only a front visor, and made of wool, cotton, etc., as a baseball cap or overseas cap, or of muslin or lace, as a nurse's or baby's cap
a special covering for the head, worn as a mark of occupation, rank, academic degree, etc.: a cardinal's cap, fool's cap
a caplike part or thing; cover or top, as the cap-shaped part of a mushroom, a small metal cover for a bottle, the cover over a camera lens or other projecting or end part, a kneecap, an artificial crown for a tooth, a mountain top, or the capital of a column