The Collaborative International Dictionary of English v.0.48:

Enlist \En*list"\, v. t. [imp. & p. p. Enlisted; p. pr. & vb.
   n. Enlisting.]
   1. To enter on a list; to enroll; to register.
      [1913 Webster]

   2. To engage for military or naval service, the name being
      entered on a list or register; as, to enlist men.
      [1913 Webster]

   3. To secure the support and aid of; to employ in advancing
      interest; as, to enlist persons in the cause of truth, or
      in a charitable enterprise.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Enlist \En*list"\, v. i.
   1. To enroll and bind one's self for military or naval
      service; as, he enlisted in the regular army; the men
      enlisted for the war.
      [1913 Webster]

   2. To enter heartily into a cause, as if enrolled.
      [1913 Webster]

WordNet (r) 3.0 (2006):

enlist
    v 1: join the military
    2: hire for work or assistance; "engage aid, help, services, or
       support" [syn: engage, enlist]
    3: engage somebody to enter the army [syn: enlist, draft,
       muster in] [ant: discharge, muster out]