1) Muscle that pushes down 
A muscle that has the action of expelling a substance. ... Origin: L. Detrudo, to drive away ... (05 Mar 2000) ... 
(de-troo´sәr) a body part that pushes down, such as a muscle. pertaining to the detrusor muscle of the bladder.
the muscle of the bladder wall
Type: Term Pronunciation: dē-trū′sŏr Definitions: 1. A muscle that has the action of expelling a substance. See: detrusor (muscle)(muscle) Type: Term Definitions: 1. the muscular coat of the urinary bladder, which, along with gravity and increased intraabdominal pressure, facilitates emptying of bladder during urination by its contraction. Synonyms: musculus detrusor vesicae
Smooth muscle layer of the bladder wall; contraction of the detrusor results in voiding of urine.
Latin detrusio = thrust away.