The Collaborative International Dictionary of English v.0.48:

Assistant \As*sist"ant\, a. [Cf. F. assistant, p. pr. of
   assister.]
   1. Helping; lending aid or support; auxiliary.
      [1913 Webster]

            Genius and learning . . . are mutually and greatly
            assistant to each other.              --Beattie.
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   2. (Mil.) Of the second grade in the staff of the army; as,
      an assistant surgeon. [U.S.]
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   Note: In the English army it designates the third grade in
         any particular branch of the staff. --Farrow.
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The Collaborative International Dictionary of English v.0.48:

Assistant \As*sist"ant\, n.
   1. One who, or that which, assists; a helper; an auxiliary; a
      means of help.
      [1913 Webster]

            Four assistants who his labor share.  --Pope.
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            Rhymes merely as assistants to memory. --Mrs.
                                                  Chapone.
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   2. An attendant; one who is present. --Dryden.
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WordNet (r) 3.0 (2006):

assistant
    adj 1: of or relating to a person who is subordinate to another
           [syn: adjunct, assistant]
    n 1: a person who contributes to the fulfillment of a need or
         furtherance of an effort or purpose; "my invaluable
         assistant"; "they hired additional help to finish the work"
         [syn: assistant, helper, help, supporter]