"Overwhelming" is an adjective, a describing word. It means "very great in amount". For instance: "his party won overwhelming support". To overwhelm means to swamp, to defeat with massively superior force, to flood over an opponent. When used to describe an emotion, it means "very strong". For instance: "she felt an overwhelming desire to giggle".

it means 'in great power/very great/intense. example: The king attacked with overwhelming force....