Contact has (or at least, use to have) at least 3 different meanings in the military flying world:
1. "Contact left 5 deg, 20 miles, 1000ft above" = I have traffic on radar (as stated).
2. "Contact Neatishead on TAD 123" = Call that GCI controller on (whatever UHF frequency Tactical Air Designator 123 decodes as). Although I thiink that was eventually changed from "contact" to "call".
3. "Contact, grid 123456" = there's a firefight at (wherever 123456 is).
And as for 'secure'..... "Secure the building" to a pongo means smash the door down, check the rooms are clear of hostiles. To a fishead it means lock the building up and b*gger off for the weekend. To the RAF it probably means make sure that we have the use of the building.