1. (Science: physiology) The tendency of some neurons to require either a stronger nerve signal or a longer recharge period before it can fire again, if it has been triggered recently.
2. (Science: psychology) The disappearance of responsiveness to accustomed stimulation. It does not include drug habituation.
Being abnormally tolerant to and dependent on something that is psychologically or physically habit-forming (especially alcohol or narcotic drugs).A general accommodation to unchanging environmental conditions.A behavioural alteration where an organism gets accustomed to a particular stimuli, and no longer produces a response to it.