noun one who or that which marks.
2. marker ·noun a counter used in card playing and other games.
3. marker ·noun one who keeps account of a game played, as of billiards.
4. marker ·noun an attachment to a sewing machine for marking a line on the fabric by creasing it.
5. marker ·noun the soldier who forms the pilot of a wheeling column, or marks the direction of an alignment.