noun. Loss of inhibition, as through the influence of external stimuli such as drugs or alcohol, or as a result of brain damage.

noun. Unrestrained behavior resulting from a lessening or loss of inhibitions or a disregard of cultural constraints.

noun. A lack or loss of inhibition.

"Psychologists call it disinhibition, and its pervasive effect—as can be witnessed every day in nasty comments appended to newspaper articles online, in the aggrieved tone and intent of some blog postings, in e-mail inboxes scorched by flame wars—has turned many parts of the Internet into a nasty place."