The extensor carpi ulnaris is a muscle located in the forearm that is responsible for extending and abducting the wrist. Synonyms for this muscle include the ulnar extensor, ulnar extensor muscle, and the extensor ulnaris muscle. Some medical professionals may refer to it as the ECU muscle or the extensor carpi ulnaris tendon when speaking specifically about the connecting tissue that attaches to the wrist and hand bones. Regardless of the term used, the extensor carpi ulnaris is an important part of forearm mobility and can be targeted with specific exercises to improve strength and functionality.