The Collaborative International Dictionary of English v.0.48:

Subjunctive \Sub*junc"tive\, a. [L. subjunctivus, fr.
   subjungere, subjunctum, to subjoin: cf. F. subjonctif. See
   Subjoin.]
   Subjoined or added to something before said or written.
   [1913 Webster]

   Subjunctive mood (Gram.), that form of a verb which express
      the action or state not as a fact, but only as a
      conception of the mind still contingent and dependent. It
      is commonly subjoined, or added as subordinate, to some
      other verb, and in English is often connected with it by
      if, that, though, lest, unless, except, until, etc., as in
      the following sentence: "If there were no honey, they
      [bees] would have no object in visiting the flower."
      --Lubbock. In some languages, as in Latin and Greek, the
      subjunctive is often independent of any other verb, being
      used in wishes, commands, exhortations, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

subjunctive mood
    n 1: a mood that represents an act or state (not as a fact but)
         as contingent or possible [syn: subjunctive mood,
         subjunctive]