How can I recover my MultiBit HD wallet words?
If you have both your wallet file (named mbhd.wallet.aes for MultiBit HD) and its password, you can use this tool to extract its mnemonic sentence/seed.

Note that the terms "brute force" and "crack" weren't the right ones to use, you're simply decrypting the wallet file. David's answer is correct in that you can't brute force a seed from scratch, but luckily that's not what you need to do here.

(Also, be sure to write your seed down somewhere once you have it! If you had lost your wallet file, you would have been out of luck...)