1. One billion (10⁹): gigahertz.
2. 1,073,741,824 (2³⁰): gigabyte.

[From Greek gigās, giant.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.