ar·ci·form (är?s?-fôrm?)adj. Formed in the shape of an arc.[Latin arci- (from arcus, bow) + -form.]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.arciform (???k??f??m) adjshaped like an archCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014