1. a pen with a thick tip for writing or drawing
2. an object used to show position or mark a boundary
3. something that indicates or identifies a particular quality or condition

Examples

• She used a red marker to highlight important information.
• The trail markers helped us find our way through the forest.
• High cholesterol is a marker for heart disease risk.
• The teacher hired additional markers to grade the final exams.
• Place a marker at the halfway point of the race course.
• He drew a map with colored markers.
• The stone marker indicated the property line.