noun

• Agent noun of block (“obstruct or prevent”); something that blocks something else.
• (sports) One who blocks or impedes the movement of an opponent.
• (computing) One who prevents another user from contacting them electronically.
• (computing) An application that stops / impedes unauthorised access to a programme.
• (computing) A bug or issue that prevents software from being released.
• (marketing) A gatekeeper who refuses the marketer access to the person they wish to contact.
• (biology, medicine) Any of various medications that block (inhibit) the activity of a chemical messenger or its receptors, such as cardiac conduction modifiers (e.g., alpha-blockers), gastric acid inhibitors (H₂ histamine blockers), puberty blockers, and others.
• A close-fitting rectangular glove worn by a goalie in multiple forms of hockey.
• (poker) A blocker bet.
• (card games) A playing card, needed by one player, that is held by another.
• A person who blocks (stretches or moulds) hats.
• A surname.