The Collaborative International Dictionary of English v.0.48:

Nonunion \Non*un"ion\, a.
   1. Not belonging to, or affiliated with, a trades union; as,
      a nonunion carpenter.
      [Webster 1913 Suppl.]

   2. Not employing trade union members; not recognizing or
      favoring trades unions or trades-unionists; as, a nonunion
      contractor; a nonunion subcontractor. -- Non*un"ion*ism,
      n.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

nonunion
    adj 1: not belonging to or not allowing affiliation with a trade
           union; "nonunion carpenters"; "a nonunion contractor"
           [ant: union]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "nonunion":
   abstraction, alienation, detachment, disarticulation,
   disassociation, disconnectedness, disconnection, discontinuity,
   disengagement, disjointing, disjunction, dislocation, disunion,
   division, divorce, divorcement, incoherence, isolation, luxation,
   parting, partition, removal, segmentation, separation, separatism,
   subdivision, subtraction, withdrawal, zoning