be on your best behaviour
to behave extremely well and be very polite on a particular occasion:
I'd just met his parents for the first time so I was on my best behaviour.
Thesaurus: synonyms and related words
Behaving well
- be (as) good as gold idiom
- behave
- best
- breeding
- child
- children should be seen and not heard idiom
- decorous
- demure
- example
- good
- gracious
- keep your nose clean idiom
- nose
- polite
- set an example idiom
- well behaved
- well bred
- well brought up
- well mannered
- well spoken