The myotome is an embryonic unit responsible for formation of the skeletal muscles of the trunk and limbs.
The term myotome is also used to describe the combination of a muscle and the nerve root which innervates it.
Finally, the term can be used to describe a surgical instrument used to incise or dissect a muscle.
Dorsal view of an embryo. The somites of the embryo, shown in red on either side of the neural tube, form the future myotomes and sclerotomes. © Gray's Anatomy, Wikimedia public domain