Definition of on one's best behavior
- The children promised to be on their best behavior.
: superlative of good
: excelling all others
: most productive of good : offering or producing the greatest advantage, utility, or satisfaction
: superlative of well
: in the best (see 1best) way : to greatest advantage
: the best (see 1best) state or part
: one that is best
: the greatest degree of good or excellence
: to get the better of : outdo
: had best (see 2best 1)
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