Hal|low|een or Hal|low|e'en «HAL oh EEN, HOL-», noun.
the evening of October 31, before Allhallows or All Saints' Day. It is observed especially by children, who masquerade, beg for treats, or play pranks.
╂[Scottish for Allhallow-even, earlier All hallow eve]
Useful english dictionary. 2012.