1. in general, the process of growing accustomed to a situation or stimulus.

2. the diminished effectiveness of a stimulus in eliciting a response, following repeated exposure to the stimulus. Compare dishabituation.

3. the process of becoming psychologically dependent on the use of a particular drug, such as cocaine, but without the increasing tolerance and physiological dependence that are characteristic of addiction; the preferred term is psychological dependence.

4. the elimination of extraneous responses that interfere with learning, through repetition and practice, a skill.