This is the 349th most frequent Swedish word.
fullt
Completely; fully; entirely.
Here, 'fullt' is used as an adjective in its neuter singular form to describe the state of the room being filled with people.
Rummet var fullt av människor.
The room was full of people.
In this example, 'fullt' functions as an adverb to mean 'completely' or 'to the fullest extent' of the action described.
Han körde fullt ut på motorcykeln.
He drove all out on the motorcycle.
Here, 'fullt' modifies the adjective 'möjligt' to intensify its meaning, working as an adverb meaning 'entirely' or 'completely'.