Meanings
outsider (who is not part of a particular group)
loner, outsider (who is socially awkward)
outcast, leper, castaway, pariah (one that has been excluded from a society or system, a pariah)
outsider, underdog, contender (who has little chance of winning)
Examples
GermanEnglish
Tom ist ein Außenseiter.Tom is an outsider.
Tom war sein Leben lang ein Außenseiter.All his life Tom was an outsider.