open up

verb11

1. •
   To open.

   • Some vacancies have opened up due to retirements.
   • Open up the door!
2. •
   To reveal (oneself); to share personal information about oneself; to become communicative.

   • After three hours of questioning, he finally opened up.
3. •
   To widen.

   • The corridor gradually opened up into a triangular room.
4. •
   To commence a literal or figurative battery of attacks.
5. •
   To commence firing weapons.

   • As the convoy entered the pass, we opened up on them with everything we had.
6. •
   To berate; to begin shouting at or insulting someone or something.

   • As soon as she saw him, she just opened up!
7. •
   (figurative) To rain.

   • The sky has really opened up. I've never seen this much rain!
8. •
   To bring up (a topic etc.).
9. •
   To begin running, driving, travelling, etc., at maximum (or faster) speed.

   • The pigeon is moving as before with unhurried haste. [...] But it must be all out. If it wasn't, then it would open up and get away from that shadow of death behind it. — 1934
10. •
    Of wine: to develop its full flavor a short time after being uncorked and poured.
11. •
    Synonym of cheat out (“to face or turn toward the audience more than would be natural”).

    • In stage acting, we are frequently asked to cheat out to the audience by opening up our body positions so that we are something halfway between facing them and our partner. — 2015