GA

Gives permission for doing something, or can be used for "egging" another person on.

GA is an acronym for "good afternoon", which is a saying typically used from noon to 5pm to greet someone. The acronym is most often seen online or in text messages.

GA is usually used in the beginning of a formal message to be polite to the recipient. It is most likely used by an older person since there are plenty of more fun and casual ways that younger people use instead.