rhom·boid (r?m?boid?)n. A parallelogram with unequal adjacent sides, especially one having oblique angles.adj. also rhom·boi·dal (-boid?l) Shaped like a rhombus or rhomboid.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.rhomboid (?r?mb??d) n (Mathematics) a parallelogram having adjacent sides of unequal lengthadj (Mathematics) having such a shape[C16: from Late Latin rhomboides, from Greek rhomboeid?s shaped like a rhombus]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014rhom?boid (?r?m b??d) n. 1. an oblique-angled parallelogram with only the opposite sides equal. 2. rhomboideus. adj. 3. Also, rhom?boi?dal. having a form similar to that of a rhombus; shaped like a rhomboid. [1560?70;