The meaning of TBDL is Teen Baby Diaper Lover.
Basically the TBDL or Teen Baby Diaper Lover is a teenager who likes dressing and acting like a baby or toddler and also loves to wear diapers.
It's basically the same thing as an ABDL which is an Adult Baby Diaper Lover.
The Adult Baby Diaper Lover is an adult who loves to dress like and act like a baby and also loves to wear diapers.
Then there are some Teens who just love to wear diapers and some adults who just love to wear diapers and not do the actually baby or toddler stuff.