"Physics is the study and application of the fundamental laws of nature, including the laws of motion, gravity, electromagnetism, heat, and microscopic interactions. These laws govern the behavior of objects at all scales, from the smallest subatomic particles to the entire observable universe. In between, physicists study nuclear reactions, the interactions of atoms with light, properties of solids, chaotic dynamics of fluids, and the evolution of stars and galaxies, among many other applications."
If this doesn't tickle your fancy, there is always the quote from Rutherford: "In science, there is only physics; all the rest is stamp collecting."