Source : Webster's Revised Unabridged Dictionary (1913)

Infrequence \In*fre"quence\, Infrequency \In*fre"quen*cy\, n.
   [L. infrequentia scantiness : cf. F. infrequence.]
   1. The state of rarely occuring; uncommonness; rareness; as,
      the infrquence of his visits.

   2. The state of not being frequented; solitude; isolation;
      retirement; seclusion. [R.]

            The solitude and infrequency of the place. --Bp.
                                                  Hall.

Source : WordNet®

infrequency
     n : noteworthy scarcity [syn: {rarity}, {rareness}]