Usually refers to someone who won't ever stop, or keeps harassing everyone.
"Stop being such a Jack!"
"Stop Jack!"
"Jack, dude, seriously, stop!"
A british jackass that annoys the fuck out of others, also known as Anon, will most likely lurk underneath your bed requesting to play video games
"That guy is such a Jack, look at him,"
"Oh yeah, he called me his m8 one day"
"he called me a faggot"
Jack is a sexy beast that can do anything he wants, when he wants including banging the hottest chicks
“Yo is there a earthquake?”
“No, It’s cause jack is here”