A quasilinear equation is one that is linear in all but the terms involving the highest order derivatives (whether they are of fractional order or not). See Quasilinear equations page to read more about them.
Note: In this category we have listed all equations which are quasilinear and NOT semilinear. Strictly speaking, all semilinear equations ought to be listed here aswell, however, as the specific methods and questions are so different in both categories (i.e. quasilinear techniques may give results for semilinear equations which are weaker when compared to the more powerful methods tailor-made for semilinear ones) we prefer to list semilinear ones in their own category only.