The Collaborative International Dictionary of English v.0.48:

Exponent \Ex*po"nent\, n. [L. exponens, -entis, p. pr. of
   exponere to put out, set forth, expose. See Expound.]
   1. (Alg.) A number, letter, or any quantity written on the
      right hand of and above another quantity, and denoting how
      many times the latter is repeated as a factor to produce
      the power indicated;

   Note: thus a^2 denotes the second power, and a^x the xth
         power, of a (2 and x being the exponents). A fractional
         exponent, or index, is used to denote the root of a
         quantity. Thus, a^1/3 denotes the third or cube root
         of a.
         [1913 Webster]

   2. One who, or that which, stands as an index or
      representative; as, the leader of a party is the exponent
      of its principles.
      [1913 Webster]

   3. one who explains, expounds, or interprets.
      [PJC]

   Exponent of a ratio, the quotient arising when the
      antecedent is divided by the consequent; thus, 6 is the
      exponent of the ratio of 30 to 5. [R.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

exponent
    n 1: a person who pleads for a cause or propounds an idea [syn:
         advocate, advocator, proponent, exponent]
    2: someone who expounds and interprets or explains
    3: a mathematical notation indicating the number of times a
       quantity is multiplied by itself [syn: exponent, power,
       index]

The Free On-line Dictionary of Computing (19 January 2023):

exponent

    (Or "characteristic") The part of a
   floating-point number specifying the power of ten by which
   the mantissa should be multiplied.  In the common notation,
   e.g. 3.1E8, the exponent is 8.

   (1995-02-27)