مَّأْكُوْلٍ

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

مَأْكُوْلٌ is the natural state of this indefinite noun and it becomes مَأْكُوْلٍ due to: 1) a preposition that precedes it or 2) a possessed noun that precedes it or 3) it’s a noun of dependent declension a) نَعْتٌ / صِفَطٌ adjectives b) التَّوْكِيْدُ emphatic c) المَعْطُوْفٌ conjunction d) البَدَلُ synonym 

and it changes to مَّأْكُوْلٍ (takes a tanween) due to the genitive noun preceding it in the sentence 

Eaten up, devoured

To eat, gnaw