A woman who is neither athletic, nor thick; but a hybrid of both. A woman who has the characteristics of a female athlete, while also possessing the shape of a voluptuous woman.
Randy: Hey Geoff, did you see that third baseman at the softball game yesterday?
Geoff: Yeah, she was quite athlethick.
Ben: I prefer women with meat on their bones and an active figure.
JJ: Oh, you mean an athlethick woman.