1. One who has had long experience in military service; an old soldier; any ex-serviceman (primarily North American).
2. The meaning of any former member of the armed forces, ex-serviceman (not necessarily old) is first recorded in 1798, in American English, but is alluded to earlier in reference to the same condition in the Roman army
3. One who has seen long service in any office or position; an experienced or aged person.