The Collaborative International Dictionary of English v.0.48:

acellular \acellular\ adj.
   1. 1 not containing cells cellular

   Syn: cell-free
        [WordNet 1.5]

   2. not made up of or divided into cells cellular

   Syn: noncellular
        [WordNet 1.5]

   3. occurring outside of cells or without the participation of
      cells. Opposite of cellular.
      [PJC]

WordNet (r) 3.0 (2006):

acellular
    adj 1: not made up of or divided into cells [syn: noncellular,
           acellular] [ant: cellular]