attention deficit hyperactivity disorder

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A syndrome, usually diagnosed in childhood, characterized by a persistent pattern of impulsiveness, a short attention span, and often hyperactivity, and interfering especially with academic, occupational, and social performance.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun neurology, pathology A developmental disorder in which a person has a persistent pattern of impulsiveness and inattention, with or without a component of hyperactivity.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a condition (mostly in boys) characterized by behavioral and learning disorders