but·ton·ball (b?t?n-bôl?)n. See sycamore.[From its button-shaped fruit.]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.buttonball (?b?t?n?b??l) n (Plants) US and Canadian a North American plane tree, Platanus occidentalis. See plane treeCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014