noun
- a person or thing that blocks.
- Football. a player whose assignment or special skill is blocking.
- Biochemistry. a substance that inhibits the physiological action of another substance, as the beta blocker propranolol that interferes with neurotransmitters in the sympathetic nervous system.
noun
- a person or thing that acts as a block
- physiol an agent that blocks a physiological function, such as the transport of an ion across an ion channel
c.1400 of a tool, c.1600 of a person, agent noun from block (v.). U.S. football sense from 1914.