A musalsal report is a transmission whose chain displays a repeated verbal or practical feature across successive narrators. The point is not simply a repeated hadith text; it is the recurrence of a particular mode or action in transmission.
For instance, one narrator says, “So-and-so told me: I heard so-and-so,” and subsequent narrators repeat the same reporting formula over several generations. That is one form of verbal seriality.
Likewise, if successive teachers perform an action while passing on the report, a practical seriality can occur. The descriptive feature of the chain must still be distinguished from the independent authenticity grade.