1. small pins with flat, round heads used to attach papers or other materials to bulletin boards or walls

Examples

• She used thumbtacks to hang her artwork on the bulletin board.
• The teacher asked students to bring thumbtacks for the classroom display.
• He accidentally stepped on a thumbtack that had fallen on the floor.
• The notice was secured to the wall with four thumbtacks.
• She removed the old thumbtacks before putting up the new poster.
• The thumbtacks came in different colors to match the decorations.