So, f'rinstance, biblical dictionaries would count, e.g. Paul J. Achtemeier, Ed., Harper's Bible Dictionary, San Francisco: Harper & Row, 1985, and John D. Davis, The Westminster Dictionary of the Bible rev. ed., Philadelphia: Westminster, 1944, as would F.L. Cross & F.A. Livingstone, Eds., The Oxford Dictionary of the Christian Church (2d ed.), London: Oxford University Press, 1974 but Michael Walsh, Ed., Dictionary of Christian Biography, Collegeville: The Liturgical Press, 2001, would not, because it contains short biographies (like in Who's Who) rather than definitions.