I. ˌsecond ˈbest 1 BrE AmE noun [uncountable]
something that you have to accept which is not perfect or not the best:
I’m not going to settle for second best.
II. ˌsecond ˈbest 2 BrE AmE adjective [only before noun] , adverb
not quite as good as the best one:
Allie was the second best shooter on the rifle team.
come off second best (=lose a game or competition, or not be as successful as someone else)