1. Cause to allow entrance or exit; allow entry after being shut
   "Mary opened up the car door";
   - open
    
2. Become open
   "The flower opened up in the morning sun";
   - open
    
3. Make available
   "This opens up new possibilities";
   - open
    
4. Become available
   "an opportunity opened up";
   - open
    
5. Open up an area or prepare a way
   "She opened up a graduate program for women students";
   - pioneer
    
6. Start to operate or function or cause to start operating or functioning
   "The new store will open up next week";
   - open
    
7. Talk freely and without inhibition
   "After a few drinks, he opened up about his past"; "She finally opened up to her therapist"
    
8. Begin firing weapons
   "The soldiers opened up on the enemy position"
    
9. [informal] Accelerate or increase speed
   "The car opened up on the highway"

Derived forms: opening up, opened up, opens up

Type of: afford, alter, arise, begin, change, change state, come up, get, get down, give, innovate, introduce, modify, mouth, set about, set out, speak, start, start out, talk, turn, utter, verbalise [Brit], verbalize, yield

Antonym: belt up [Brit, informal]

Encyclopedia: Open up, yoga hoser!