Definitions
1.nounA slit in a castle wall; today, any similar window for shooting a ranged weapon or letting in light.
2.nounA method of escape, especially an ambiguity or exception in a rule or law that can be exploited in order to avoid its effect.
3.verbTo prepare a building for defense by preparing slits or holes through which to fire on attackers
4.verbTo exploit (a law, etc.) by means of loopholes.