1. Third person singular present indicative reflexive form of 'formar' with 'rugas' as object; describes the process of wrinkles appearing or developing on skin
As we age, wrinkles form on our face.
Com a idade, forma-se rugas no nosso rosto.
2. Can also refer to the formation of creases or folds in fabric or other materials
If you don't iron properly, wrinkles form in the fabric.
Se não passar bem a roupa, forma-se rugas no tecido.