adumbration (n.)

1550s, "faint sketch, imperfect representation," from Latin adumbrationem (nominative adumbratio) "a sketch in shadow, sketch, outline," noun of action from past-participle stem of adumbrare "to cast a shadow, overshadow," in painting, "represent (a thing) in outline," from ad- "to" (see ad-) + umbrare "to cast in shadow," from PIE root *andho- "blind; dark" (see umbrage).