The Collaborative International Dictionary of English v.0.48:

nonparticipation \nonparticipation\ n.
   withdrawing from the activities of a group.

   Syn: non-engagement, non-involvement.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

nonparticipation
    n 1: withdrawing from the activities of a group [syn: non-
         engagement, nonparticipation, non-involvement] [ant:
         engagement, involution, involvement, participation]