Georgia law does not define a cracked windshield.
What the Official Code of Georgia Annotated (OCGA) does state in Section 40-8-73 if a windshield is damaged in a certain way that the car is not to be driven. Subsection e of this portion of GA law says that no motor vehicle shall be operated with a windshield or rear window having a starburst or spider webbing effect greater than three inches by three inches.
If police see this type a crack that is larger than 3" by 3" they can ticket you under this section of the OCGA. As crazy as it sounds, this type of traffic offense is considered a misdemeanor which in GA can come with a maximum penalty of fine of up to $1000 and/or up to 12 months imprisonment.
This Georgia windshield offense though normally comes with just a fine being assigned to it. For instance, the Athens-Clarke County Court notes on their site that the fine given ere for a conviction of this violation is $110.
If you have a cracked windshield that needs to be repaired or replaced and you have comprehensive insurance on your vehicle, then you can make a claim under this portion of your car insurance policy. Your Comprehensive deductible amount will be due but above that amount your car insurance company should pay the remainder of what it costs to fix your windshield.