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.