pa·pav·er·ine (p?-p?v??-r?n?, -?r-?n)n. A nonnarcotic alkaloid obtained from the opium poppy, C20H21NO4, structurally distinct from morphine and other opiates, used in its hydrochloride form to relieve spasms of smooth muscle.[Latin pap?ver, poppy + -ine.]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.papaverine (p??pe?v??ri?n; -r?n) n (Elements & Compounds) a white crystalline almost insoluble alkaloid found in opium and used as an antispasmodic to treat coronary spasms and certain types of colic. Formula: C20H21NO4[C19: from Latin pap?ver poppy]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014pa?pav?er?ine (p??pæv ??rin, -?r ?n, p??pe? v??rin, -v?r ?n) n. a white, crystalline alkaloid, C20H21NO4, used as a smooth-muscle relaxant. [1855?60;