A needle without an eye (usually) made of drawn-out steel wire with one end sharpened and the other flattened or rounded into a head, used for fastening.

A small nail with a head and a sharp point.

A cylinder often of wood or metal used to fasten or as a bearing between two parts.

“Pull the pin out of the grenade before throwing it at the enemy.”

(often followed by a preposition such as "to" or "on") To fasten or attach (something) with a pin.

(usually in the passive) To cause (a piece) to be in a pin.

To pin down (someone).