Pirate Outposts in Far Cry 3 have an alarm system.
If enemies spot you, they will attempt to sound the alarm and it will say "Alarm Triggered"
When the alarm sounds, all pirates will be alerted to your presence - not just the ones inside the camp, but also others who are near the area or on patrol
To prevent the sounding of the alarm, you should either kill the pirates stealthily, disable the alarms via the Alarm Box, or shoot them before they can reach the alarm control panel.
