The term mutate refers to most non-mutant superbeings in the Marvel Comics universe. See below for other uses.
Mutate is a term used in Marvel Comics to refer to superhumans who acquired their superpowers by exposure to some mutagenic compound or energy (either accidentally or deliberately). Unlike Marvel's Mutants, Mutates require external stimuli to acquire their powers (i.e. they weren't born with the potential to manifest powers). Within the Earth X universe, the powers and abilities of Earth's mutates and mutants alike are the direct result of the genetic manipulations of the Celestials in humanity's distant past, who placed dormant genes within one cross-section of humanity, and the active Deviant and Eternal genes in other cross-sections.