What is the meaning of the word "lock"?

Definitions:

become engaged or intermeshed with one another verb
- They were locked in embrace
become rigid or immoveable verb
- The therapist noticed that the patient's knees tended to lock in this exercise
fasten with a lock verb
- lock the bike to the fence
hold fast in a certain state verb
- I was locked in a laughing fit.
put in a place where something cannot be removed or someone cannot escape verb
- The parents locked their children up for the weekend.
to hold in a locking position verb
- They locked their hands around the boulder.