The Collaborative International Dictionary of English v.0.48:

euphoric \euphoric\ adj.
   strongly experiencing a feeling of well-being; feeling
   euphoria. Opposite of dysphoric. [Narrower terms:
   expansive]

   Syn: elated, happy.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Expansive \Ex*pan"sive\ ([e^]ks*p[a^]n"s[i^]v), a. [Cf. F.
   expansif.]
   1. Having a capacity or tendency to expand or dilate;
      diffusive; of much expanse; wide-extending; as, the
      expansive force of heat; the expansive quality of air.
      [WordNet sense 1]
      [1913 Webster]

            A more expansive and generous compassion. --Eustace.
      [1913 Webster]

            His forehead was broad and expansive. --Prescott.

   2. causing expansion; as, the expansive force of heat.
      [1913 Webster +PJC]

   3. of much expanse; wide-extending; as, an expansive view of
      the mountains.
      [PJC]

   4. friendly, open, and unrestrained in conversation or
      discourse; -- of people; as, wine made the guest
      expansive. [WordNet sense 4]

   Syn: effusive, talkative.
        [WordNet 1.5]

   5. characterized by exaggerated feelings of euphoria and
      delusions of grandeur. [WordNet sense 3]
      [WordNet 1.5] -- Ex*pan"sive*ly, adv.
      -Ex*pan"sive*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

expansive
    adj 1: able or tending to expand or characterized by expansion;
           "Expansive materials"; "the expansive force of fire"
           [ant: unexpansive]
    2: of behavior that is impressive and ambitious in scale or
       scope; "an expansive lifestyle"; "in the grand manner";
       "collecting on a grand scale"; "heroic undertakings" [syn:
       expansive, grand, heroic]
    3: marked by exaggerated feelings of euphoria and delusions of
       grandeur
    4: friendly and open and willing to talk; "wine made the guest
       expansive" [syn: expansive, talkative]

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "expansive":
   accessible, affable, airy, all jaw, all-embracing, all-inclusive,
   amiable, ample, amplitudinous, approachable, big, bouncy, broad,
   buoyant, candid, capacious, chatty, commodious, communicable,
   communicative, comprehensive, conversable, conversational, copious,
   deep, demonstrative, dilatable, dilatant, distensive, easy,
   effervescent, effusive, elastic, enlarging, expandable, expanding,
   expansible, expansile, expansional, extendable, extended,
   extending, extensible, extensile, extensional, extensive,
   extroverted, far-reaching, flip, fluent, frank, free,
   free-speaking, free-spoken, free-tongued, friendly, full, gabby,
   garrulous, gassy, generous, genial, glib, gossipy, great,
   gregarious, gushy, infinite, inflatable, inflationary, large,
   lavish, liberal, long-winded, loquacious, multiloquent,
   multiloquious, newsy, open, openhanded, outgoing, outspoken,
   overtalkative, prolix, resilient, roomy, scopic, self-revealing,
   self-revelatory, smooth, sociable, spacious, spreading, talkative,
   talky, unconstrained, unhampered, unrepressed, unreserved,
   unrestrained, unrestricted, unreticent, unsecretive, unshrinking,
   unsilent, unsuppressed, vast, verbose, volatile, voluble,
   voluminous, warm, wide, wide-ranging, widespread, windy