pa·pil·i·o·na·ceous (p?-p?l??-?-n??sh?s)adj. Having a bilaterally symmetrical corolla somewhat resembling a butterfly, characteristic of certain plants of the pea family such as a sweet pea.[Latin p?pili?, p?pili?n-, butterfly; see pavilion + -aceous.]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.papilionaceous (p??p?l???ne???s) adjshaped or in the form of a butterflyCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014pa?pil?i?o?na?ceous (p??p?l i ??ne? ??s) adj. having an irregular corolla shaped like a butterfly, as the pea and other leguminous plants. [1660?70;