A trocar is a sharp-pointed surgical instrument, used to puncture a body cavity for fluid aspiration. It is used with a cannula to be inserted into a vein, artery, bone marrow or body cavity. It is a very sharply pointed shaft, with a three-sided point.
The word trocar is derived from the French "trois" (three) + "carre" (side). It is used for exploring purposes or inserting drainage tubes etc.