Bad debt according to Robert Kiyosaki is a money loaned to buy things that takes money out of your pocket (liability).
One example is when I get a loan to buy a brand new sports car for my personal enjoyment. Since that sports car doesn't put money into my pocket, or simply I don't earn from it then it's a Bad debt.
The other debt is called Good Debt. (what most rich people have) Good debt is the opposite of bad debt.
When I get a loan to buy a rental apartment and if from that apartment, I receive monthly income from my tenants...that's a Good debt.
Do you know now what to avoid?