The Collaborative International Dictionary of English v.0.48:

dactyl \dac"tyl\ (d[a^]k"t[i^]l), n. [L. dactylus, Gr. da`ktylos
   a finger, a dactyl. Cf. Digit.]
   1. (Pros.) A poetical foot of three sylables (--- [crescent]
      [crescent]), one long followed by two short, or one
      accented followed by two unaccented; as, L.
      t["e]gm[i^]n[e^], E. mer[bprime]ciful; -- so called from
      the similarity of its arrangement to that of the joints of
      a finger. [Written also dactyle.]
      [1913 Webster]

   2. (Zool.)
      (a) A finger or toe; a digit.
      (b) The claw or terminal joint of a leg of an insect or
          crustacean.
          [1913 Webster]

WordNet (r) 3.0 (2006):

dactyl
    n 1: a metrical unit with stressed-unstressed-unstressed
         syllables
    2: a finger or toe in human beings or corresponding body part in
       other vertebrates [syn: digit, dactyl]