Someone that enjoys doing things indoors, including video games, using the computer, or just watching TV. People usually think indoor kids are awkward or anti-social or out of shape but that in fact is not true. Indoor kids enjoy hanging out with others just indoors. Usually indoor kids start being indoor kids from a very young age.
A: Hey, man wanna go rock climbing?
B: Nah, lets play call of duty instead. You know im an indoor kid.