Sometimes 'out of bounds' refers to unwritten rules about areas or topics you should avoid. Discussing someone's salary is considered out of bounds in many cultures.
Pro Tip 2/3
Privacy Respect
'Out of bounds' can indicate respect for privacy, signaling areas you shouldn't enter without permission. The diary on her desk is out of bounds to us; don't even think about peeking.
Pro Tip 3/3
Cultural Sensitivity
Be aware that 'out of bounds' areas can vary across cultures, indicating cultural sensitivities. In some societies, asking about one's personal life is out of bounds.