- Emerging from the light of the sun, or passing into it;
rising or setting at the same, or nearly the same, time as the sun.
Meaning of 'heliacal' (Princeton's WordNet)
1 . heliacal
[ a]
Meaning (1): - 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
Example in sentence:
the heliacal or Sothic year is determined by the heliacal rising of Sothis (the Egyptian name for the Dog Star);