noun

• The fully shaded inner region of a shadow cast by an opaque object.
• (astronomy) The area on the earth or moon experiencing the total phase of an eclipse.
• (astronomy) The central region of a sunspot.
• (chiefly literary) A shadow.
• (archaic) An uninvited guest brought along by one who was invited.
• One of the family Umbridae of mudminnows.
• One of genus Umbrina of drums (family Sciaenidae).
• (mathematics) An element of the umbral calculus.