Adjective second best has 1 sense
  1. second-best - next to the best; "his second-best bed"
    Antonym: worst (indirect, via best)
,Adverbial second best has 1 sense
  1. second-best - in second place; "he came off second-best"
,Noun second best has 1 sense
  1. runner-up, second best - the competitor who finishes second
    --1 is a kind of rival, challenger, competitor, competition, contender
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