To reply all is to answer a message to everybody who received it. Hit reply all, do not reply all, an accidental reply all.
It is the commonest office mistake there is, and one careless reply all can generate hundreds of messages. The rule is to use it only when everybody genuinely needs the answer.
1phrasereply allTo answer a message to everybody who received it.
“He meant to answer one person and pressed reply all instead.”
reply all is an action.
Practised in Office & Admin