Definition of mesectoderm in US English:

mesectoderm

noun

Embryology
  • Mesenchyme that is derived from ectoderm or the neural crest rather than from mesoderm. Also: the outer layer of blastoderm before its differentiation into ectoderm and mesoderm.

Origin

Late 19th century; earliest use found in Journal of the Royal Microscopical Society. From German Mesektoderm from Meso- + Ektoderm.