The forearm is comprised of two bones, the radius and the ulna. The ulna is the bigger bone of the forearm and articulates with the humerus at the elbow joint. The process at the proximal end of it is the olecranon.
The olecranon is the large curved bony process of the ulna at the elbow. It is opposite to the cubital fossa, which is the depression in front of the elbow. When the hand is in supination position the olecranon is facing towards the back. The posterior surface of the olecranon is smooth and covered by a bursa. The anterior surface forms the upper portion of the semilunar notch.
A related term is the olecranal that is a descriptive word relating to or pertaining to olecranon.