A completely awesome guy who is loved by all, girls want to be around him, and guys want to be him. Kieran's have large penis's and often find it hard to stay faithful to one girl as there are so many offering themselves up to him.
Girl 1: Oh my god check that guy out
Girl 2: Yeah, he's a kieran.
Girl 1: Oh, he must have a big dick then, let's dance naked around him and have sex with him.