<p><strong>Verb</strong></p><ul><li>to move or distract from the main subject or course.</li><li>to move from the main track to a siding, as a train.</li></ul><p><strong>Noun</strong></p><ul><li>any railroad track, other than a siding, that is auxiliary to the main track.</li><li>a path, position, project, topic, etc., of less importance than the main one: On a sidetrack to this thread on workplace safety, let me just say a little about office footwear.</li></ul>