The Collaborative International Dictionary of English v.0.48:

Archangel \Arch`an"gel\, n. [L. archangelus, Gr. 'archa`ggelos:
   cf. OF. archangel, F. archange. See Arch-, pref., and
   Angel.]
   1. A chief angel; one high in the celestial hierarchy.
      --Milton.
      [1913 Webster]

   2. (Bot.) A term applied to several different species of
      plants (Angelica archangelica, Lamium album, etc.).
      [1913 Webster]

WordNet (r) 3.0 (2006):

archangel
    n 1: an angel ranked above the highest rank in the celestial
         hierarchy
    2: a biennial cultivated herb; its stems are candied and eaten
       and its roots are used medicinally [syn: garden angelica,
       archangel, Angelica Archangelica]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "archangel":
   angel, angel of light, angel of love, angelology, angels,
   archangels, beatified soul, canonized mortal, celestial, cherub,
   cherubim, dominations, dominions, heavenly being, martyr,
   messenger of God, patron saint, powers, principalities,
   principality, recording angel, saint, saved soul, seraph, seraphim,
   soul in glory, thrones, virtues



Easton's 1897 Bible Dictionary:

Archangel
   (1Thess. 4:16; Jude 1:9), the prince of the angels.