What does "myotome" mean?

Myotome: (a) A muscular segment; one of the zones into which the muscles of the trunk, especially in fishes, are divided; a myocomma. (b) One of the embryonic muscular segments arising from the protovertebræ; also, one of the protovertebræ themselves. (c) The muscular system of one metamere of an articulate.