someone who just appears to be there without invitation or invites them self sometimes in an unwanted situation but it is possible to ring in with friends if you see them down the street thus accompaning them but generally ringing in seeing as you were not invited
"hey can i ring in with you guys"
can also be :
ringing in "that dude is always ringing in"
rings in " fred always just rings in "
kinda like gate crashing but not in more of an everyday life sence