Pronunciation: (blok'ur), [key]
1. a person or thing that blocks.
2. Football.a player whose assignment or special skill is blocking.
3. Biochem.a substance that inhibits the physiological action of another substance, as the beta blocker propranolol that interferes with neurotransmitters in the sympathetic nervous system.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.