side·car (s?d?kär?)n.1. A one-wheeled car for a single passenger, attached to the side of a motorcycle.2. A cocktail combining brandy, an orange-flavored liqueur, and lemon juice.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.sidecar (?sa?d?k??) n1. (Automotive Engineering) a small car attached on one side to a motorcycle, usually for one passenger, the other side being supported by a single wheel2. (Brewing) a cocktail containing brandy with equal parts of Cointreau and lemon juiceCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014side?car (?sa?d?k?r) n. 1. a one-passenger car at the side of a motorcycle. 2. a cocktail of brandy, orange liqueur, and lemon juice. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.