noun Someone or something that is markedly unusual or unpredictable.
The two-headed calf was a freak.
noun A person who is extremely abnormal in appearance, social behavior, sexual orientation, gender identity, or business practices; an oddball, a unique person, originally in a displeasing or alienating way.
noun A hippie.
noun A drug addict.
noun A person whose physique has grown far beyond the normal limits of muscular development; often a bodybuilder weighing more than 260 pounds (120 kg).
noun An enthusiast, or person who has an obsession with, or extreme knowledge of, something.
Bob's a real video-game freak. He owns every games console of the last ten years.