let rip
to do something without restraint
I give a dinner party for ten people about every three weeks. It's a big number where I can really let rip and make things look beautiful.
to suddenly start talking about something that you feel strongly about but had previously been quiet about
He sometimes wondered if it wouldn't be better if she let rip as she used to do over his inadequacies in the past.
Easy Learning Idioms Dictionary. Copyright © HarperCollins Publishers