word-by-word since any text will be split into words anyway. And all EU languages into English only

Well, then you should probably start building your multilingual dictionary. I don't think Google Translate would be too happy about you making thousands of automated single-word queries.

Eurovoc: http://eurovoc.europa.eu/drupal/?q=download/list_pt&cl=en
CPV: http://simap.europa.eu/codes-and-nomenclatures/codes-cpv/codes-cpv_en.htm
Other EU term lists: http://ec.europa.eu/eurostat/ramon/nomenclatures/index.cfm?TargetUrl=LST_NOM&StrGroupCode=CLASSIFIC&StrLanguageCode=EN

Add whatever you can extract from Wikipedia and Wiktionary dumps and you should be set.