\Bi*fi"lar\, a. [Pref. bi- + filar.]
Two-threaded; involving the use of two threads; as, bifilar
suspension; a bifilar balance.
{Bifilar micrometer} (often called {a bifilar}), an
   instrument form measuring minute distances or angles by
   means of two very minute threads (usually spider lines),
   one of which, at least, is movable; -- more commonly
   called a {filar micrometer}.