paribhāṣā: what does it mean?

There seem to be at lest two technical meanings of paribhāṣā, one pointing to its use as general exegetical rule and the other as metarule. The second one is most of all typical of Pāṇini's Grammar, or better of the exegesis of his grammar, since Pāṇini himself never uses this term. The first one is common in Śrautasūtra commentaries and in the exegesis of Mīmāṃsā.

Why this difference? In my opinion, because Pāṇini's grammar entails both the operational rules and the metarules organizing them, whereas the Mīmāṃsāsūtra has before it already all the operational rules, scattered in the Brāhmaṇas and thus, its rules are bound to be general rules and not metarules.