zygosphene (?za?????sfi?n) n (Zoology) zoology a linking part of the vertebrae of snakes and lizards which fits into a zygantrumCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014