1) an expedition, campaign, military service, warfare
2) metaphorically Paul likens his contest with the difficulties that oppose him in the discharge of his apostolic duties, as warfare
Part of Speech: noun feminine
Citing in TDNT: 7:701, 1091
From G4754; military service, that is, (figuratively) the apostolic career (as one of hardship and danger): - warfare.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root στρατεία; click on the second column to search for that grammatical form of the root στρατεία; click on the third column to search for that word and grammatical form; click on the total to search for the root στρατεία.