bi·filar \(ˈ)bī+\adjective Etymology: International Scientific Vocabulary bi- (I) + fil- (from Latin filum thread) + -ar — more at file 1.: composed of or employing two threads or wires < a bifilar suspension of a waving part of an instrument > 2.: composed of or employing a single thread or wire doubled back upon itself < bifilar winding of a resistance coil > • bi·filarlyadverb