eruptionsudden, violent outburst; ejection of molten rock or steam from a volcano or geyserNot to be confused with:irruption ? a breaking or bursting in; a violent incursion or invasionAbused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embreee·rup·tion (?-r?p?sh?n)n.1. a. The act or process of erupting.b. An instance of erupting.2. A sudden, often violent outburst.3. a. An appearance of a rash or blemish on the skin.b. Such a rash or blemish.4. The emergence of a tooth through the gums.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.e?rup?tion (??r?p ??n) n. 1. an issuing forth suddenly and violently; outburst; outbreak. 2. the ejection of molten rock, steam, etc., as from a volcano or geyser. 3. something that is erupted or ejected, as molten rock. 4. a. the breaking out of a rash or the like. b. the rash itself. 5. the emergence of a growing tooth through the gum tissue. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.