This is a man that is over 30 years of age that spends his time playing video games online. This person can be very responsible individuals but at times can act just like a kid thefore resulting in the term man kid.
A man kid can be spotted playing Call of Duty, Madden NFL Football, etc. They also like to wear headsets and refer to the time spent online as "gaming."
by Wife of Man Kid November 17, 2011
substitute for son. refers to a child in middle age
Finally, my mankid is coming to visit Australia!,
by aussie mom August 23, 2011