What does the term "bad debt collection" mean?

I think, from where you've heard the term, is basically about debt collectors who don't follow FDCPA rules to collect debts. For example, they may call the debtors at midnight or threaten for the collection of the unpaid amount.
If you face such a situation, you can file a complaint with the CFPB online. You can also contact your state's attorney general and file a complaint.

There is yet another definition of this term. Bad debt collection or bad debt recover refers to the payments received after a debt has been charged off and has been declared uncollectible. Even after a debt has been charged off or written off, collection efforts can continue to receive payments.

Some debt collection practices are illegal. For example, calling the debtor all the time, disturbing, abusing, and threatening. If you are facing this kind of things, then make a complaint against them.

Bad debt collection means the payments which have been received by the collection agency after a debt has been charged off and considered as uncollectible.