This is the 5276th most frequent Russian word.
огромную
"Огромную" means "huge" or "enormous" in English.
The word 'огромную' here is an adjective in the accusative case modifying the direct object 'книгу'.
Она купила огромную книгу.
She bought a huge book.
In this sentence, 'огромную' functions as an adjective modifying 'коллекция' in the accusative case.
На столе лежала огромную коллекция монет.
A huge collection of coins was lying on the table.
The word 'огромную' acts as an adjective in the accusative case modifying 'толпу' as the direct object of the verb 'встретили'.