Source : Webster's Revised Unabridged Dictionary (1913)

Big \Big\, a. [Compar. {Bigger}; superl. {Biggest}.] [Perh. from
   Celtic; cf. W. beichiog, beichiawg, pregnant, with child, fr.
   baich burden, Arm. beac'h; or cf. OE. bygly, Icel. biggiligr,
   (properly) habitable; (then) magnigicent, excellent, fr. OE.
   biggen, Icel. byggja, to dwell, build, akin to E. be.]
   1. Having largeness of size; of much bulk or magnitude; of
      great size; large. ``He's too big to go in there.''
      --Shak.

   2. Great with young; pregnant; swelling; ready to give birth
      or produce; -- often figuratively.

            [Day] big with the fate of Cato and of Rome.
                                                  --Addison.

   3. Having greatness, fullness, importance, inflation,
      distention, etc., whether in a good or a bad sense; as, a
      big heart; a big voice; big looks; to look big. As applied
      to looks, it indicates haughtiness or pride.

            God hath not in heaven a bigger argument. --Jer.
                                                  Taylor.

   Note: Big is often used in self-explaining compounds; as,
         big-boned; big-sounding; big-named; big-voiced.

   {To talk big}, to talk loudly, arrogantly, or pretentiously.

            I talked big to them at first.        --De Foe.

   Syn: Bulky; large; great; massive; gross.

Bigger \Big"ger\, a.,
   compar. of {Big}.

Source : WordNet®

big
     adj 1: above average in size or number or quantity or magnitude or
            extent; "a large city"; "set out for the big city"; "a
            large sum"; "a big (or large) barn"; "a large family";
            "big businesses"; "a big expenditure"; "a large number
            of newspapers"; "a big group of scientists"; "large
            areas of the world" [syn: {large}] [ant: {small}, {small}]
     2: significant; "graduation was a big day in his life"
     3: of very great significance; "deciding to drop the atom bomb
        was a very big decision"; "a momentous event" [syn: {momentous}]
     4: conspicuous in position or importance; "a big figure in the
        movement"; "big man on campus"; "he's very large in
        financial circles"; "a prominent citizen" [syn: {large}, {prominent}]
     5: very intense; "a bad headache"; "in a big rage"; "had a big
        (or bad) shock"; "a bad earthquake"; "a bad storm" [syn: {bad}]
     6: loud and firm; "a big voice"; "big bold piano sounds"
     7: prodigious; "big spender"; "big eater"; "heavy investor"
        [syn: {big(a)}, {heavy(a)}]
     8: (of animals) fully developed; "an adult animal"; "a grown
        woman" [syn: {adult}, {full-grown}, {fully grown}, {grown},
         {grownup}]
     9: marked by intense physical force; "a big wind"
     10: feeling self-importance; "too big for his britches"; "had a
         swelled head"; "he was swelled with pride" [syn: {swelled},
          {vainglorious}]
     11: older brother or sister; "big sister" [syn: {big(a)}, {elder},
          {older}] [ant: {little(a)}]
     12: exhibiting self-importance; "big talk" [syn: {boastful}, {braggart(a)},
          {bragging(a)}, {braggy}, {cock-a-hoop}, {crowing}, {self-aggrandizing},
          {self-aggrandising}]
     13: generous and understanding and tolerant; "a heart big enough
         to hold no grudges"; "that's very big of you to be so
         forgiving"; "a large and generous spirit"; "a large
         heart"; "magnanimous toward his enemies" [syn: {large}, {magnanimous}]
     14: given or giving freely; "was a big tipper"; "the bounteous
         goodness of God"; "bountiful compliments"; "a freehanded
         host"; "a handsome allowance"; "Saturday's child is
         loving and giving"; "a liberal backer of the arts"; "a
         munificent gift"; "her fond and openhanded grandfather"
         [syn: {bighearted}, {bounteous}, {bountiful}, {freehanded},
          {handsome}, {giving}, {liberal}, {openhanded}]
     15: in an advanced stage of pregnancy; "was big with child";
         "was great with child" [syn: {big(p)}, {enceinte}, {expectant},
          {gravid}, {great(p)}, {large(p)}, {heavy(p)}, {with
         child(p)}]
     [also: {biggest}, {bigger}]

bigger
     adj : large or big relative to something else [syn: {larger}]

big
     adv 1: extremely well; "his performance went over big"
     2: in a boastful manner; "he talked big all evening" [syn: {boastfully},
         {vauntingly}, {large}]
     3: on a grand scale; "think big" [ant: {small}]
     4: in a major way; "the play failed big at the box office"
     [also: {biggest}, {bigger}]

bigger
     See {big}