No, a white dwarf is not bigger than a main sequence star. In fact, white dwarfs are the final stage in the evolution of stars that are not massive enough to become neutron stars or black holes. They are very dense, with a mass similar to that of the Sun but a volume that is only about the size of the Earth. This means that they have a surface gravity that is much stronger than that of the Sun. Main sequence stars, on the other hand, are stars that are still burning hydrogen in their cores and have a surface gravity that is similar to that of the Sun.