Overactive bladder: A sudden involuntary contraction of the muscular wall of the bladder causing urinary urgency, an immediate unstoppable need to urinate. It is a form of urinary incontinence (the unintentional loss of urine) and affects about 1 in 11 adults, particularly older adults. Treatment may include pelvic muscle strengthening, behavioral therapy, and medications. Also called urge incontinence.
