A person that gets flustered very easily.
Person 1: Hey, looking really good and sexy today!
Person 2: Th-thanks.. *currently blushing*
Person 1: You're such a "blush baby!"
A blush baby is someone who easily gets flustered.
Person 1: You look really good today!
Person 2: Th-thanks.. *currently blushing*
Person 1: Wow, you're a blush baby!