You are no fun

The origin of this phrase "you got no jams" comes from korean word "재미 (jaemi)" which means "fun". Jaemi and jams sound familiar, so Rap Monster put jams instead of Jaemi in the sentence making it funnier.

P.S : In korean, "you got no jams" is "너 재미없어 (neo jaemi obseo)"

A very terrible insult. If you have no jams, on a scale of Jimin to Namjoon, you are Jimin.

The highest level of insult possible.
Literally meaning you have no fun. You are a lifeless peice o' shit.

U have become a jamless person in life.

If someone says this to you, don't take it as an insult. Think of it this way, a cute, priceless baby that we musthink protecthe at all costs was told the same thing. Consider yourself lucky!!