1) A transgender
person who was born biologically male but identifies as being a female. Usually a t-girl has undergone breast implant surgery or takes hormones to grow the breasts, but will retain the penis. IE: A chick with a dick.
2) One who wishes to be considered by society as a member of the opposite sex. Their personal identification and psychological configuration is that of the opposite sex. They prefer to act and dress like a woman.
A t-girl is also known as a chick with a dick.