The Omnia online dictionary defines [non-]Polish words [and expressions] in Polish, and thus is not of much use to those who do not know that language—except that it also includes etymologies, so if you have even a basic acquaintance with Slavic it serves as a fine companion to etymological dictionaries for other Slavic languages (like mine for Russian and Czech). And it seems to cast its net quite widely, judging from the fact that it has an entry for scouse, “bryt. ang. slang, dialekt mieszkaƒców Liverpoolu (miasto w Lancashire na zach. wybrze´´u Êrodk. Anglii).” The main problem is the special Polish characters, which (as you can see) do not reproduce well, and which I have no idea how to input into the search box, so that I can’t look up (for instance) the word slowo ‘word’ (which has a barred l, pronounced /w/) [and which is probably not there anyway, being Polish]. If anyone knows how to do this, the info will be much appreciated.