What does a gay "a spot" mean?

The male equivalent of the G Spot, found in the vagina for woman.

Definition

The special spot in men, located in the rectum, that provides ultimate pleasure when properly stimulated through touch by another, or by one's self.

The term "A-spot" does not refer to a widely recognized concept in male sexuality. And normaly referring to the "A-spot" in female sexuality, which stands for the anterior fornix erogenous zone. This is a sensitive area located deep within the vagina, towards the cervix.