What's the meaning of “cap”

Question

On the surface, this Labor Day holiday caps another dark year for unions and many working-class Americans. -NY Times

I found the meaning of it in the dictionary like the below but I don't know which one is correct.

1.[VERB] [usu passive] [BRIT] If a sports player is capped, they are chosen to represent their country in a team game such as football, rugby, or cricket.

2.[VERB] If the government caps an organization, council, or budget, it limits the amount of money that the organization or council is allowed to spend, or limits the size of the budget.

3.[VERB] [JOURNALISM] If someone says that a good or bad event caps a series of events, they mean it is the final event in the series, and the other events were also good or bad.

4.[VERB] [usu passive] If someone's teeth are capped, covers are fixed over them so that they look better.

Answer 1

3 is the closest meaning for the context of your example. If you want another example to help try this one.

'I stubbed my toe this morning, then the wind blew away my scarf, the coffee pot at work was empty and to cap it all, there were five bills to pay when I got home. '

In this context, as in your example, CAP simply means 'the rounding off', or 'closing', of a series of events. Typically cap is used in this context with 'it all' or 'off' and usually has a negative connotation.

I hope this helps.

Answer 2

Like @StoneyB said, it's closet to #3.

I think using "closes" instead of "caps" would work just as fine in this case.

Just like you close a water bottle by putting the cap on. So capping can by synonym of closing.

So in the context of your example, it's just saying it's closing/capping out the previous year (since last labor day) till this labor day.