not open (one's) mouth

(redirected from didn't open his mouth)

not open (one's) mouth

To be completely silent; to remain discreet (about something); to not tell anyone (about something). All the while our teacher was shouting at us, we didn't open our mouths. Don't open your mouth about this! I would die of embarassment if anyone were to find out.
See also: mouth, not, open
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