What is "heliac"

Heliac \He"li*ac\, a. Heliacal.

a. (alternative form of heliacal English)

adj. pertaining to or near the sun; especially the first rising of a star after and last setting before its invisibility owing to its conjunction with the sun; "the heliacal rising of the Dog Star"; "the heliacal or Sothic year is determined by the heliacal rising of Sothis (the Egyptian name for the Dog Star)" [syn: heliacal]