WordNet (r) 3.0 (2006):

beta-adrenergic blocking agent
    n 1: any of various drugs used in treating hypertension or
         arrhythmia; decreases force and rate of heart contractions
         by blocking beta-adrenergic receptors of the autonomic
         nervous system [syn: beta blocker, beta-blocking agent,
         beta-adrenergic blocker, beta-adrenergic blocking
         agent]