The Collaborative International Dictionary of English v.0.48:

Truancy \Tru"an*cy\, n.
   The act of playing truant, or the state of being truant; as,
   addicted to truancy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

truancy
    n 1: failure to attend (especially school) [syn: truancy,
         hooky]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "truancy":
   AWOL, French leave, abscondence, absence, absence without leave,
   absentation, absenteeism, absenting, clock-watching, cut, day off,
   default, departure, disappearance, dodging, ducking, escape,
   excused absence, fleeing, furlough, goofing off, holiday, hooky,
   leave, leave of absence, leaving, malingering, nonappearance,
   nonattendance, running away, sabbatical leave, shirking,
   sick leave, skulking, slacking, soldiering, tax dodging,
   tax evasion, truantism, unexcused absence, vacation, welshing