The Collaborative International Dictionary of English v.0.48:

Next \Next\ (n[e^]kst), a., superl. of Nigh. [AS. n[=e]hst,
   ni['e]hst, n[=y]hst, superl. of ne['a]h nigh. See Nigh.]
   1. Nearest in place; having no similar object intervening.
      --Chaucer.
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            Her princely guest
            Was next her side; in order sat the rest. --Dryden.
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            Fear followed me so hard, that I fled the next way.
                                                  --Bunyan.
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   2. Nearest in time; as, the next day or hour.
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   3. Adjoining in a series; immediately preceding or following
      in order.
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            None could tell whose turn should be the next.
                                                  --Gay.
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   4. Nearest in degree, quality, rank, right, or relation; as,
      the next heir was an infant.
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            The man is near of kin unto us, one of our next
            kinsmen.                              --Ruth ii. 20.
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   Note: Next is usually followed by to before an object, but to
         is sometimes omitted. In such cases next in considered
         by many grammarians as a preposition.
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   Next friend (Law), one who represents an infant, a married
      woman, or any person who can not appear sui juris, in a
      suit at law.
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WordNet (r) 3.0 (2006):

next friend
    n 1: (law) a person who acts on behalf of an infant or disabled
         person

Bouvier's Law Dictionary, Revised 6th Ed (1856):

NEXT FRIEND. One who, without being regularly appointed guardian, acts for
the benefit of an infant, married woman, or other person, not sui juris.
Vide Amy; Prochein Amy.