What does the Phrase "Knock for Six" mean ?

Question

In what context(s) is it applicable?

Answer 1

To "knock someone for six" means to surprise and upset someone a lot. Example: It really knocked me for six when my ex-boyfriend announced he was getting married.

- From http://idioms.thefreedictionary.com/knock+for+six

Answer 2

it's a term used in cricket. it you hit the ball over the outer boundary without it touching the ground, you get 6 runs. so say if someone hits you really hard or tells you something that totally astounds you, you are "knocked for six", gettit?

Answer 3

When you achieve something