Definition of "sidetrack"

sidetrack

noun
plural sidetracks
1. (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. (sometimes) Any auxiliary railroad track, as differentiated from a siding, that runs adjacent to the main track.
3. (mining) A smaller tunnel or well drilled as an auxiliary off a main tunnel or well.
4. 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.
  Quotations
  "However, I am down a side-track. What I wanted to say to you is that you must not take Bolsover's little spirit circus too seriously."
  1925 July – 1926 May, A[rthur] Conan Doyle, “(please specify the chapter number)”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019
verb
third-person singular simple present sidetracks, present participle sidetracking, simple past and past participle sidetracked
1. (rail transport) To divert (a locomotive or train) on to a lesser used track in order to allow other trains to pass.
  Quotations
  It was just after 5 p.m.; would the non-stop "Capitals Limited" come up next? It was due in at 5.30 and other trains are often side-tracked in its favour.
  1951 January, R. A. H. Weight, “A Railway Recorder in Essex and Hertfordshire”, in Railway Magazine, page 46
  Two westbound freights were in the vicinity and the operator was kept busy passing them radio messages with the latest information on the late running of the streamliners, to allow the enginemen to keep moving until the last possible minute before they had to sidetrack their trains to let the fast trains overtake.
  1961 July, J.Geoffrey Todd, “Impressions of railroading in the United States: Part Two”, in Trains Illustrated, page 423
2. 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.
3. To sideline; to push aside; to divert or distract from, reducing (something) to a secondary or subordinate position.
4. (intransitive) To deviate briefly from the topic at hand.