This is the 16409th most frequent Polish word.
wasza
"Wasza" means "your" (plural or formal) in Polish.
Here, 'wasza' is a possessive pronoun used to indicate that the book belongs to a group of people being addressed informally.
Czy to jest wasza książka?
Is this your book?
In this case, 'wasza' refers to a collaborative effort or task that a addressed group completed.
Wasza praca była bardzo dobra!
Your work was very good!
Here, 'wasza' is used possessively to indicate that the proposal belongs to or is attributed to the group being addressed.