rhomboid vs rhomboidal

rhomboid

adj
  • resembling, or shaped like a rhombus or rhomboid 

noun
  • A solid shape which has rhombic faces 

  • Any of several muscles that control the shoulders 

  • A parallelogram which is neither a rhombus nor a rectangle 

rhomboidal

adj
  • rhomboid, having a rhomboid shape 

How often have the words rhomboid and rhomboidal occurred in a corpus of books? (source: Google Ngram Viewer )