sidetrack

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To divert from a main issue or course: I was sidetracked from my work by an unexpected visitor.
2. v. To delay or block the progress of deliberately: "a bill that would sidetrack food irradiation in this country” ( Alexis Beck).
3. v. To switch from a main railroad track to a siding.
4. v. To deviate from a main issue or course.
5. v. To run into a siding.
6. n. A railroad siding.

Century Dictionary and Cyclopedia

1. n. A short line of rails branching off by a switch from the main line of a railroad, and either returning to it or not at the further end, for use in turning out, shifting rolling-stock, etc.; a siding.
2. To put upon a side-track; shift from the main line of a railroad to a subsidiary one; shunt.
3. Figuratively, to divert to one side; turn aside from the proper or the practicable course.
4. To pass to a side-track; come to rest on a siding.

Wiktionary

1. n. rail transport A second, relatively short length of track just to the side of a railroad track, joined to the main track by switches at one or both ends, used either for unloading freight, or to allow two trains on a same track to meet (opposite directions) or pass (same direction); a railroad siding.
2. n. Any auxiliary railroad track, as differentiated from a siding, that runs adjacent to the main track.
3. n. mining A smaller tunnel or well drilled as an auxiliary off a main tunnel or well.
4. n. An alternate train of thought, issue, topic, or activity, that is a deviation or distraction from the topic at hand or central activity, and secondary or subordinate in importance or effectiveness.
5. v. To divert (a locomotive) on to a lesser used track in order to allow other trains to pass.
6. v. To divert or distract (someone) from a main issue or course of action with an alternate or less relevant topic or activity; or, to use deliberate trickery or sly wordplay when talking to (a person) in order to avoid discussion of a subject.
7. v. To sideline; to push aside; to divert or distract from, reducing (something) to a secondary or subordinate position.
8. v. intransitive To deviate briefly from the topic at hand.

GNU Webster's 1913

1. v. (Railroads) To transfer to a siding from a main line of track.
2. v. colloq. Hence, fig., to divert or reduce to a position or condition that is relatively secondary or subordinate in activity, importance, effectiveness, or the like; to switch off; to turn aside, as from a purpose.

WordNet 3.0

1. v. wander from a direct or straight course
2. n. a short stretch of railroad track used to store rolling stock or enable trains on the same line to pass