Infrequent, mild language such as "damn" and "hell," as well as some name-calling.
The term "Oh my God" is used several times throughout the movie.
The old man verbally abuses the mother of the wolf children based off of her ignorance to farming and constant smiling. Some examples: "Damn fool" and "lunatic".
(Note: The above only applies to the English language dub; the subtitle track contains no such language. It is likely that the old man is simply talking down to her in a disrespectful, Japanese conjugation, for which there is no easy English substitute.)