Wordnet 3.0
NOUN (2)
1. 
 a period of time assigned for work; 
- Example: "they work long hours"2. 
 an indefinite period of time; 
- Example: "they talked for hours"
The Collaborative International Dictionary of English v.0.48:
Hours \Hours\, n. pl. [A translation of L. Horae (Gr. ?). See
   Hour.] (Myth.)
   Goddess of the seasons, or of the hours of the day.
   [1913 Webster]
         Lo! where the rosy-blosomed Hours,
         Fair Venus' train, appear.               --Gray.
   [1913 Webster]
WordNet (r) 3.0 (2006):
hours
    n 1: a period of time assigned for work; "they work long hours"
    2: an indefinite period of time; "they talked for hours"