In the "umbrae Idearum" he initiates the work of reconstruction, giving colour to his thought and sketching his idea.
1590s, "phantom, ghost," a figurative use from Latin umbra "shade, shadow" (see umbrage). Astronomical sense of "shadow cast by the earth or moon during an eclipse" is first recorded 1670s. Meaning "an uninvited guest accompanying an invited one" is from 1690s.
Plural umbras or umbrae (ŭm'brē)