Source : WordNet®

GB
     n 1: a highly toxic chemical nerve agent that inhibits the
          activity of cholinesterase [syn: {sarin}]
     2: a unit of magnetomotive force equal to 0.7958 ampere-turns
        [syn: {gilbert}, {Gi}]
     3: a unit of information equal to one billion (1,073,741,824)
        bytes or 1024 megabytes [syn: {gigabyte}, {G}]
     4: a monarchy in northwestern Europe occupying most of the
        British Isles; divided into England and Scotland and Wales
        and Northern Ireland [syn: {United Kingdom}, {UK}, {Great
        Britain}, {Britain}, {United Kingdom of Great Britain and
        Northern Ireland}]

Source : Free On-Line Dictionary of Computing

GB
     
         {gigabytes} or {gigabits} - see {MB}.  Giga stands for
        10^9 - a US billion, or in computing for 2^30.
     
        The text of a thirty volume encyclopaedia would require about
        one gigabyte of {ASCII} storage.
     
        (1997-03-27)

Gb
     
         Gigabit.  10^9 {bit}s.  Might also be wrongly used for
        {gigabyte} ({GB}).
     
        (1997-03-27)

gb
     
         (Great Britain) A {country code} for United
        Kingdom.  "{uk}" is generally used instead.
     
        (1999-01-27)