The Collaborative International Dictionary of English v.0.48:

Unifilar \U`ni*fi"lar\, a. [Uni- + L. filum a thread.]
   Having only one thread; involving the use of only one thread,
   wire, fiber, or the like; as, unifilar suspension.
   [1913 Webster]

   Unifilar magnetometer (Physics), an instrument which
      consists of a magnetic bar suspended at its center of
      gravity by a long thread, constituting a delicate means
      for accurately measuring magnetic intensities, also for
      determining declinations of the magnetic needle.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unifilar
    adj 1: having or using only one filament