rhomboideus (r?m?b??d??s) n, pl -dei (-d??a?) (Anatomy) anatomy either of two muscles that connect the spinal vertebrae to the scapulae[C19: New Latin, from Late Latin rhomboides: see rhomboid]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014rhom?boi?de?us (r?m?b?? di ?s) n., pl. -de?i (-di?a?) either of two back muscles that function to move the scapula. [1825?35;