Source : Webster's Revised Unabridged Dictionary (1913)

Whitmonday \Whit"mon`day\, n. (Eccl.)
   The day following Whitsunday; -- called also {Whitsun
   Monday}.

Source : WordNet®

Whitsun Monday
     n : the day after Whitsunday; a legal holiday in England and
         Wales and Ireland [syn: {Whitmonday}]