The Collaborative International Dictionary of English v.0.48:

Myrmidon \Myr"mi*don\, n. [L. Myrmidones, Gr. Myrmido`nes, pl.]
   1. One of a fierce tribe or troop who accompanied Achilles,
      their king, to the Trojan war.
      [1913 Webster]

   2. A soldier or a subordinate civil officer who executes
      cruel orders of a superior without protest or pity; --
      sometimes applied to bailiffs, constables, etc.
      --Thackeray.
      [1913 Webster]

            With unabated ardor the vindictive man of law and
            his myrmidons pressed forward.        --W. H.
                                                  Ainsworth.
      [1913 Webster]

WordNet (r) 3.0 (2006):

myrmidon
    n 1: a follower who carries out orders without question
    2: (Greek mythology) a member of the warriors who followed
       Achilles on the expedition against Troy

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "myrmidon":
   adherent, assistant, creature, dependent, disciple, dummy,
   employee, feudatory, figurehead, flunky, follower, gillie,
   girl Friday, goon, hanger-on, henchman, hired hand, hired man,
   hireling, homager, inferior, jackal, lackey, liege, liege man, man,
   man Friday, mercenary, minion, pensioner, peon, puppet, retainer,
   right-hand man, satellite, serf, slave, stooge, subordinate,
   sycophant, thug, underling, understrapper, vassal, votary, worker,
   yeoman



The Devil's Dictionary (1881-1906):

MYRMIDON, n.  A follower of Achilles -- particularly when he didn't
lead.