Tadpole

A young man (usually in his 20s) who has the maturity of a much younger person and generally acts like a bratty child. They typically make themselves known in a loud and annoying manner, often while playing video games and using the voice chat.

Player 1 (22 year old man): "Squeeeeeee you guys are LAME. Such LOSERS. GG EZ git gud."
Player 2 (30 year old man): "Sounds like we have a real tadpole on our team gents."