ADHD definitions

WordNet (r) 3.0 (2005)

n
1: a condition (mostly in boys) characterized by behavioral and learning disorders [syn: attention deficit disorder, ADD, attention deficit hyperactivity disorder, ADHD, hyperkinetic syndrome, minimal brain dysfunction, minimal brain damage, MBD]

Merriam Webster's

abbreviation attention deficit/hyperactivity disorder

Collin's Cobuild Dictionary

ADHD is an abbreviation for attention deficit hyperactivity disorder.