Source : WordNet®

gigabyte
     n : a unit of information equal to one billion (1,073,741,824)
         bytes or 1024 megabytes [syn: {G}, {GB}]

Source : Free On-Line Dictionary of Computing

gigabyte
     
         2^30 = 1,073,741,824 {byte}s = 1024 {megabytes}.
     
        Roughly the amount of data required to encode a human gene
        sequence (including all the redundant codons).
     
        See {prefix}.
     
        (1995-09-29)