tertium quid: Meaning and Definition of

ter•ti•um quid

Pronunciation: (tûr'shē-um kwid' Lat. ter'ti-&oobrevem&sec kwid'), [key]
  1. something related in some way to two things, but distinct from both; something intermediate between two things.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.