GHz

1. Short for gigahertz, GHz is a unit of measurement for alternating current (AC) or electromagnetic (EM) wave frequencies equal to 1,000,000,000 Hz. 
2. When referring to a computer processor or CPU, GHz is a clock frequency, also known as a clock rate or clock speed, representing a cycle of time. An oscillator circuit supplies a small amount of electricity to a crystal each second that is measured in MHz or GHz, where "Hz" is the abbreviation of Hertz, "M" representing Mega, or one million, and "G" representing Giga, or one thousand million. In addition to GHz and MHz, there is KHz, or 1,000 Hz. 

Also see: CPU, MHz, KHz, Hertz, Processor definitions