i·bu·pro·fen (??byo?o-pr??f?n)n. A nonsteroidal anti-inflammatory drug, C13H18O2, commonly used for its analgesic and antipyretic properties. [Alteration of i(so)bu(tyl)phen(yl) pro(pionic acid).]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.ibuprofen (a?bju??pr??f?n) n (Pharmacology) a drug, isobutylphenylpropionic acid, that relieves pain and reduces inflammation: used to treat arthritis and muscular strains. Formula: C13H18O2Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014i?bu?pro?fen (?a? byu?pro? f?n) n. a nonsteroidal anti-inflammatory drug, C13H18O2, used esp. for reducing local pain and swelling, as of the joints. [1965?70; isobutylphenyl propionic acid] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.i·bu·pro·fen (??byo?o-pr??f?n) A medicine used to reduce fever, pain, or inflammation.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.