結局 (けっきょく、kekkyoku) means "after all, eventually."
I like this word and am blogging it today because it gets used with a very exasperated intonation at times. I was listening to my girlfriend tell me a story about her workday, all in English, and she gets near the end of the story, doesn't know the word she wants to use in English, and sighs in a very "I'm so fed up at this point" kind of way - 結局 (haha I can italicize it).
Anyway - that's how it came out.
I think the best way to think of this word is to imagine a very unhappy girlfriend or a rather irritated boyfriend using it as a one-word exclamation - Finally! - with hands thrown up in the air where appropriate in your personal situation.
Grammatically you can use it to introduce a new sentence as in:
ハンバーグかパスタで迷って、結局、パスタを食べた（ハンバーグかパスタでまよって、けっきょく、パスタをたべた) - I was stuck between pasta and hamburger (for dinner), but finally (at last), I had pasta.
And that's the word of the day!