Technically, borrowing from a library is also 'being in debt', but no one considers themselves to be "in debt" to a library they're currently borrowing from, because there's no accrued 'interest', you just bring the items back at the specified time.

Using a credit card over the month and paying the exact same amount at the end of it, as you would have paid piece by piece over the month had you been using cash, is essentially the same thing.