Pronunciation: (sing'gul-trak'), [key]
1. (of a railroad or section of a railroad's route) having but one set of tracks, so that trains going in opposite directions must be scheduled to meet only at points where there are sidings.
2. having a narrow scope; one-track: He has a single-track mind.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.