The Collaborative International Dictionary of English v.0.48:

Nominal \Nom"i*nal\, a. [L. nominalis, fr. nomen, nominis, name.
   See Name.]
   1. Of or pertaining to a name or names; having to do with the
      literal meaning of a word; verbal; as, a nominal
      definition. --Bp. Pearson.
      [1913 Webster]

   2. Existing in name only; not real; as, a nominal difference.
      "Nominal attendance on lectures." --Macaulay.
      [1913 Webster]

   4. Hence: Insignificant; trifling; -- of prices or costs, as
      compared with the benefits gained; as, to pay a nominal
      sum for the data; a nominal fee.
      [PJC]

   3. Within acceptable limits; as expected; as, the hydraulic
      lines are at nominal pressure; -- used mostly in aviation
      and space operations.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Nominal \Nom"i*nal\, n.
   1. A nominalist. [Obs.] --Camden.
      [1913 Webster]

   2. (Gram.) A verb formed from a noun.
      [1913 Webster]

   3. A name; an appellation.
      [1913 Webster]

            A is the nominal of the sixth note in the natural
            diatonic scale.                       --Moore
                                                  (Encyc. of
                                                  Music. )
      [1913 Webster]

WordNet (r) 3.0 (2006):

nominal
    adj 1: relating to or constituting or bearing or giving a name;
           "the Russian system of nominal brevity"; "a nominal lists
           of priests"; "taxable males as revealed by the nominal
           rolls"
    2: insignificantly small; a matter of form only (`tokenish' is
       informal); "the fee was nominal"; "a token gesture of
       resistance"; "a toknenish gesture" [syn: nominal,
       token(a), tokenish]
    3: pertaining to a noun or to a word group that functions as a
       noun; "nominal phrase"; "noun phrase"
    4: of, relating to, or characteristic of an amount that is not
       adjusted for inflation; "the nominal GDP"; "nominal interest
       rates" [ant: real]
    5: named; bearing the name of a specific person; "nominative
       shares of stock" [syn: nominative, nominal]
    6: existing in name only; "the nominal (or titular) head of his
       party" [syn: nominal, titular]
    n 1: a phrase that can function as the subject or object of a
         verb [syn: noun phrase, nominal phrase, nominal]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "nominal":
   abstract noun, adherent noun, adjectival, adverbial, alleged,
   apparent, attributive, budget, byname, cheap, cognominal,
   collective noun, common noun, conjunctive, copulative, correct,
   diminutive, easy, economic, economy, epithetic, formal, frugal,
   functional, gerund, glossematic, grammatic, honorific,
   hypocoristic, hypostasis, in name only, inconsiderable,
   inexpensive, insignificant, insubstantial, intransitive, linking,
   low, low-priced, manageable, minimal, minor, minuscule, moderate,
   modest, nominative, noun, noun phrase, ostensible, participial,
   postpositional, prepositional, pretended, professed, pronominal,
   pronoun, proper noun, proposed, propositional, puppet, purported,
   quasi, quotation noun, reasonable, representational, seeming,
   self-called, self-christened, self-styled, sensible, shabby,
   shoddy, small, so-called, soi-disant, structural, substantive,
   supposed, supposititious, syntactic, tagmemic, tiny, titular,
   token, transitive, trifling, trivial, unexpensive, verbal,
   within means, worth the money, would-be