n 1  :  the increase in intensity of a reflex when the initiating stimulus is prolonged without alteration of intensity due to the activation of increasing numbers of motoneurons - compare REINFORCEMENT   2  :  an abnormally rapid increase in the sensation of loudness with increasing sound intensity that occurs in deafness of neural origin and esp. in neural deafness of the aged in which soft sounds may be completely inaudible while louder sounds are distressingly loud .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.