spasmo-

A spasm.

Greek spasmos, spasma, from span, pull.

In medicine, a spasmolytic (Greek lusis, loosening) is a drug that relieves spasms of smooth muscle; a spasmogen is a substance that can produce smooth muscle contractions; spasmophilia is an undue tendency of the muscles to contract. The usual adjective relating to spasms is spasmodic, which also has a general sense of something that happens intermittently.