A metric prefix denoting 1,000,000,000 (one billion, or 109) units. In computing, giga- refers to 230, and one gigabyte (GB) of storage is approximately equal to one billion bytes of data (actually 1,073,741,824 bytes). See Metric Prefix. See also Kilo-, Mega-, Tera-, Peta-, and Exa-. Giga- is usually abbreviated G.