Hello Zabuch, sorry for taking so long to answer. The iARPA formatis described in the IRSTLM manual: http://hermes.fbk.eu/people/bertoldi/teaching/img/irstlm-manual.pdf
You could use that to build a dictionary, but depending on what exactly you mean by "dictionary" (i.e., depending on how close you are to traditional, papel dictionaries) using the Wiktionary as a corpus would be much better, not to mention using parallel language links from the English Wikipedia to the other ones (it has the great advantage of having almost no noise).
I'm sorry I am not able to help you more, please give me an example of what you really mean and I might be able to help more. Best regards, tresoldi (talk) 17:22, 23 May 2010 (UTC)