Definition of thumbtack in English English dictionary
A small nail-like tack with a slightly rounded head that can be pressed into place with light pressure from the thumb; used for hanging light articles on a wall or noticeboard
A thumbtack is a short pin with a broad flat top which is used for fastening papers or pictures to a board, wall, or other surface. a short pin with a flat top that is used for fixing notices on walls British Equivalent: drawing pin
a tack for attaching papers to a bulletin board or drawing board fasten with thumbtacks; "The teacher thumbtacked the notice on the bulletin board