'eye opener' definitions:

Definition of 'eye opener'

From: WordNet
noun
An alcoholic drink intended to wake one up early in the morning
noun
Something surprising and revealing

Definition of 'eye opener'

From: GCIDE
  • eye opener \eye opener\ n.
  • 1. That which makes the eyes open, as startling news or occurrence; something which causes one to suddenly understand what was not previously known. [1913 Webster]
  • 2. A drink of liquor, especially the first one in the morning. [U. S. Slang] [1913 Webster]