This is a french slang word wich is commonly used in the expression "N'importe nawak !" or shortly "Nawak !". This is derived from the familiar expression "N'importe quoi !" which itself is derived from "Tu dis n'importe quoi !" which means "You're talking nonsense !".
To resume, we can say that "Nawak !" Cpould be traduced bye "Nonsens !" if this expression exists in english. I don't know then cause i'm french...
Tu dis vraiment nawak. T'es trop chelou.