مُّؤْصَدَةٌ

A word in the Arabic language will either be 1) a verb or 2) a noun or 3) a particle – مُّؤْصَدَةٌ is a noun

A noun may either be 1) Definite or indefinite 2) Masculine or feminine 3) Singular, dual or plural 4) Nominative, accusative or genitive

مُؤْصَدَةٌ is the natural state of this indefinite noun and it is in this state ( مَرْفُوْعٌ) when the noun is: 1) the subject المُبْتَدَأُ or 2) the predicate الخَبَرُ or 3) اسْمُ كَانَ or 4) خَبَرُ إِنَّ or 5) الفَاعِلُ subject of a verb in the active voice or 6) نَائِبُ الفَاعِلِ subject of a verb in the passive voice or 7) it’s a noun of dependent declension a) نَعْتٌ / صِفَطٌ adjectives b) التَّوْكِيْدُ emphatic c) المَعْطُوْفٌ conjunction d) البَدَلُ synonym

مُؤْصَدَةٌ takes a shaddah and changes to مُّؤْصَدَةٌ due to an indefinite noun or a word ending in مِيْمٌ preceding it in the sentence

Closed over (a fire, the heat of which is not allowed to escape and no one can get out)

To be fast, firm, remain in a place, build a store, enclosure, close (a door) stop, shut