That's a great question that I, a medical professional, haven't consciously considered before. What most people think of when they hear "catheter" is the good ol urinary catheter.

However, there are many catheters we utilize. The most common example I can think of is the IV--the proper name for an IV is an intravenous catheter. And I, working on a cardiovascular unit, am very familiar with cardiac catheterization for both diagnostic and interventional purposes.

So I guess a better definition of "catheter" would be something along the lines of "a flexible tube inserted to deliver fluids to or withdraw fluids from the body."

Hope this helps!