I have heard that it is the Greek word for gospel and means good news of military victory, though many websites i have looked at say it is merely good news. Is that so?
εὐαγγέλιον can mean a few different (but related) things. It helps to understand that the word is made up of two components:
εὖ - "good" or "well" (as in 'I am well')
*ἀγγελιον - is not quite a word by itself, but it's related to ἀγγέλλω which is a verb meaning 'to announce, declare, relate'. -ἀγγελιον is thus 'something announced'.
εὐαγγέλιον can mean: (1) some good news brought as a declaration. (2) This includes news of a military victory. (3) In the Christian sense it refers to very specific 'good news', which I will come back to, (4) It's also used for the announcement of an emperor's accession to the throne, (5) in older Greek (pre-New-Testament), it can mean a reward or a religious offering given because of good news.
The term 'gospel' in English is itself a fairly direct rendering of 'good news', being constucted from god as a spelling for 'good', and spel for 'story, message'. It is an old-English word that in our times only means the Christian 'good news'.