Bas·tille Day (b?-st?l?)n. July 14, observed in France in commemoration of the storming of the Paris Bastille by the citizens of Paris at the outset of the French Revolution (1789).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.Bastille Day n (in France) an annual holiday on July 14, commemorating the fall of the Bastille Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Bastille? Day` n. July 14, a French national holiday commemorating the fall of the Bastille in 1789. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.