Source : Webster's Revised Unabridged Dictionary (1913)

Vanilla \Va*nil"la\, n. [NL., fr. Sp. vainilla, dim. of Sp.
   vaina a sheath, a pod, L. vagina; because its grains, or
   seeds, are contained in little pods.]
   1. (Bot.) A genus of climbing orchidaceous plants, natives of
      tropical America.

   2. The long podlike capsules of {Vanilla planifolia}, and {V.
      claviculata}, remarkable for their delicate and agreeable
      odor, for the volatile, odoriferous oil extracted from
      them; also, the flavoring extract made from the capsules,
      extensively used in confectionery, perfumery, etc.

   Note: As a medicine, vanilla is supposed to possess powers
         analogous to valerian, while, at the same time, it is
         far more grateful.

   {Cuban vanilla}, a sweet-scented West Indian composite shrub
      ({Eupatorium Dalea}).

   {Vanilla bean}, the long capsule of the vanilla plant.

   {Vanilla grass}. Same as {Holy grass}, under {Holy}.

Source : WordNet®

vanilla
     n 1: any of numerous climbing plants of the genus Vanilla having
          fleshy leaves and clusters of large waxy highly fragrant
          white or green or topaz flowers
     2: a flavoring prepared from vanilla beans macerated in alcohol
        (or imitating vanilla beans) [syn: {vanilla extract}]
     3: a distinctive fragrant flavor characteristic of vanilla
        beans

Source : Free On-Line Dictionary of Computing

vanilla
     
        1. (Default flavour of ice cream in the US) Ordinary
        {flavour}, standard.  When used of food, very often does not
        mean that the food is flavoured with vanilla extract!  For
        example, "vanilla wonton soup" means ordinary wonton soup, as
        opposed to hot-and-sour wonton soup.  Applied to hardware and
        software, as in "Vanilla {Version 7} {Unix} can't run on a
        vanilla {PDP 11}/34."  Also used to orthogonalise chip
        nomenclature; for instance, a 74V00 means what TI calls a
        7400, as distinct from a 74LS00, etc.  This word differs from
        {canonical} in that the latter means "default", whereas
        vanilla simply means "ordinary".  For example, when hackers go
        to a chinese restaurant, hot-and-sour wonton soup is the
        {canonical} wonton soup to get (because that is what most of
        them usually order) even though it isn't the vanilla wonton
        soup.
     
        [{Jargon File}]
     
        (1994-11-04)
     
        2. {Snobol4} by {Catspaw, Inc.} for {MS-DOS}.
     
        {(ftp://cs.arizona.edu/snobol4/vanilla.arc)}.
     
        (1992-02-05)