oddball

Compound of odd +‎ ball. Attested since the 1940s, with the adjective appearing earlier than the noun.

• (US) IPA^(key): /ˈɑːdˌbɔl/

oddball (plural oddballs)

1. An eccentric or unusual person.
   • 1964, Earl Warren et alia, Report of the President's Commission on the Assassination of President John F. Kennedy‎, page 685:

     Miss Quinn thought that Oswald spoke Russian well in view of his lack of formal training; she found the evening uninteresting. Donovan, with whom she had a date later, testified that she told him that Oswald was “kind of an oddball.”

   • 1989, Maris Soule, Storybook Hero, page 5:

     "She's different, mister. A real oddball, if you know what I mean. But your little girl would love her. All kids love the Doll Lady."

2. (neuroscience) A deviant stimulus that appears among repetitive stimuli during an experiment, to trigger an event-related potential in the participant.

• weirdo
• black sheep, odd fish, strange fish, queer fish

oddball (not comparable)

1. Exotic, not mainstream.
   • 1984, Steven K. Roberts, The Complete Guide to Microsystem Management:

     An oddball word processor, for example, might never be supported by such helpful tools as spelling checkers, indexing programs, footnote utilities,...