The Collaborative International Dictionary of English v.0.48:

Archdeacon \Arch`dea"con\, n. [AS. arcediacon, archidiacon, L.
   archidiaconus, fr. Gr. ?. See Arch-, pref., and Deacon.]
   In England, an ecclesiastical dignitary, next in rank below a
   bishop, whom he assists, and by whom he is appointed, though
   with independent authority. --Blackstone.
   [1913 Webster]