Real Dictionary

catheter
countable noun: A catheter is a tube which is used to introduce liquids into a human body or to withdraw liquids from it.

catheter in American English
a slender, hollow tube, as of metal or rubber, inserted into a body passage, vessel, or cavity for passing fluids, making examinations, etc., esp. one for draining urine from the bladder
noun: a flexible or rigid hollow tube employed to drain fluids from body cavities or to distend body passages, esp. one for passing into the bladder through the urethra to draw off urine or into the heart through a leg vein or arm vein for diagnostic examinatio

catheter in British English
noun: a long slender flexible tube for inserting into a natural bodily cavity or passage for introducing or withdrawing fluid, such as urine or blood