What is the meaning of the word "shock"?

Definitions:

a bushy thick mass of something, especially hair noun
- They had an unruly shock of black hair.
a reflex response to the passage of electric current through the body noun
- subjects received a small electric shock when they made the wrong response
an instance of agitation of the earth's crust noun
- the first shock of the earthquake came shortly after noon while workers were at lunch
an unpleasant or disappointing surprise noun
- It came as a shock to learn that our favorite restaurant had closed.
collect or gather into shocks verb
- shock grain
strike with disgust or revulsion verb
- The dog might shock the kids.
strike with horror or terror verb
- The news of the bombing shocked her
the violent interaction of individuals or groups entering into combat noun
- the armies met in the shock of battle