The Collaborative International Dictionary of English v.0.48:

Adherent \Ad*her"ent\, a. [L. adhaerens, -entis, p. pr.: cf. F.
   adh['e]rent.]
   1. Sticking; clinging; adhering. --Pope.
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   2. Attached as an attribute or circumstance.
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   3. (Bot.) Congenitally united with an organ of another kind,
      as calyx with ovary, or stamens with petals.
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The Collaborative International Dictionary of English v.0.48:

Adherent \Ad*her"ent\, n.
   1. One who adheres; one who adheres; one who follows a
      leader, party, or profession; a follower, or partisan; a
      believer in a particular faith or church.
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   2. That which adheres; an appendage. [R.] --Milton.
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   Syn: Follower; partisan; upholder; disciple; supporter;
        dependent; ally; backer.
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WordNet (r) 3.0 (2006):

adherent
    adj 1: sticking fast
    n 1: someone who believes and helps to spread the doctrine of
         another [syn: disciple, adherent]

The Devil's Dictionary (1881-1906):

ADHERENT, n.  A follower who has not yet obtained all that he expects
to get.