combination lock
nounUK /ˌkɒmbɪˈneɪʃən lɒk/
US /ˌkɑːmbɪˈneɪʃən lɑːk/
A combination lock is a lock that opens when you turn its dials to the right secret numbers.
She spun the dials on her combination lock to open her school locker.
OTHER MEANINGS
2. A lock opened by pressing a correct sequence of buttons or numbers.
The bike's combination lock clicked open after he entered 4-2-7.
3. Any locking device whose key is a secret series of symbols rather than a physical key.
The suitcase had a small combination lock built into the zipper.
4. Figuratively, a tricky problem that needs the right set of steps to solve.
Figuring out the schedule felt like cracking a combination lock.