Someone who consistently and often quite thirstily posts self-photographs on Instagram.
Mary-Katherine posted three photos of herself on Instagram today; therefore, Mary-Katherine is an Instawhore.
Generally females in the age group of 12-17 who participate in the social medium which is familiar to hipsters and food fanatics: Instagram. Instawhores compete against each other to take the most revealing photos of themselves. These photos are usually followed-up by numerous amounts of hashtags (such as '#Swag' and '#YOLO').
Jess: Hey Krystal, let's have a competition to see who can take the most amount of pictures of ourselves with barely any clothes on before our accounts get reported.
Krystal: Oh my gosh! That would be so awesome! We're gonna be such Instawhores. YOLO!