thun·der·storm (th?n?d?r-stôrm?)n. A transient, sometimes violent storm of thunder and lightning, often accompanied by rain and sometimes hail.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.thunderstorm (???nd??st??m) n (Physical Geography) a storm caused by strong rising air currents and characterized by thunder and lightning and usually heavy rain or hailCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014thun?der?storm (???n d?r?st?rm) n. a transient storm of lightning and thunder, usu. with rain and gusty winds. [1645?55] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.thun·der·storm (th?n?d?r-stôrm?) A storm of heavy rain accompanied by lightning and thunder and sometimes hail.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.