A metric prefix denoting 1,000,000,000,000,000,000 (one quintillion, or 1018) units. In computing, exa- refers to 260, and one exabyte (EB) of storage (should such a thing exist some day) is approximately equal to one quintillion bytes of data (actually 1,152,921,504,606,846,976 bytes). See Metric Prefix. See also Kilo-, Mega-, Giga-, Tera-, and Peta-. Exa- is usually abbreviated E.