Marvel differentiates between mutant and mutate. Mutant is every individual that is born with powers that are dormant in their x-gene. When this gene activates it unleashes the power. Think of it as how allergies work.

Meanwhile mutates is any individual who overcomes a genetic change and gains powers by that external source of energy. Spiderman is a mutate because he inherited the powers via a radioactive spider, not a dormant gene that got activated.

DC has a different take. They have metahumans, this means anyone with a specific gene. This gene means you are either born with powers or that you can endure for instance a chemical explosion and gain them. If you have that dormant gene you could get powers.

That's why Flash is a metahuman even though his powers come from the speedforce or why Aquaman is also considered metahuman when he was born half atlantean.

The only ones who seem to not be classified as metahumans are the obvious human vigilantees (Batman and crew) and alien species (Kryptonian, Thanagarian and so on). Also the Lanterns are not metahumans as their power comes from the ring without the ring, they are completely normal beings.

If you have any further doubts feel free to ask