catheter Definition

a tubular medical device for insertion into canals, vessels, passageways, or body cavities usually to permit injection or withdrawal of fluids or to keep a passage open

a catheter with an inflatable tip which can be expanded (as by air or water) especially to hold the catheter in place or to expand a partly closed or obstructed bodily passage, opening, or vessel (such as a coronary artery) —called also balloon-tipped catheter

a thin, flexible catheter used especially to drain urine from the bladder by way of the urethra