Emily Dickinson Lexicon

A-CRON'IC, or A-CRON'IC-AL, a. [Gr. ακρος, extreme, and νυξ, night.]

In astronomy, a term applied to the rising of a star at sun-set, or its setting at sun-rise. This rising or setting is called acronical. The word is opposed to cosmical. – Bailey. Encyc. Johnson.