n :  any of various compounds with a structure that consists essentially of four pyrrole rings joined by four =CH- groups : esp  :  one (as chlorophyll or hemoglobin) containing a central metal atom and usu. having biological activity .
 
 
 
Similar sounding terms:  para·phre·nia  par·ooph·o·ron  peri·ovar·i·an 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2004.