A term of encouragement often used to drunkenly encourage equally intoxicated acquaintances. Rarely used on the subject of encouragement's actual birthdate. Commonly preceeded by "Go (name)" and occasionally followed by, "no it's not, go anyway" when spoken by those in the 8-13 year old age bracket (who are hopefully not drunk).
"Look, Susan's about to dance on the bar!"
"Go Susan, it's your birthday!"