Dictionary.net

• mon-[=o]-blas'tik, adj. pertaining to that condition of the metazoic embryo in which a single germinal layer is alone represented.

1908 - Chambers's Twentieth Century Dictionary of the English Language
By Thomas Davidson

• Pertaining to the single germinal layer that succeeds segmentation in the ovum. [Gr.]

1916 - Appleton's medical dictionary
By Smith Ely Jelliffe