What is the meaning of the word superfluous in this sentence? All of the superfluous items in Marco's backpack made it difficult for him to carry it.

Superfluous in that sentence means "unnecessary." Just fit the word in and it works!

All of the unnecessary items in Marco's backpack made it difficult for him to carry it.

(No wonder why he was discovered bitten in half.)

In this case, you could see it means "heavy" as it was describing the items and the sentence stated that the items were hard to carry, so therefore we could think that the word superfluous means heavy.; 3