a small or narrow opening, as in a wall, for looking through, for admitting light and air, or, particularly in a fortification, for the discharge of missiles against an enemy outside.
a means of escape or evasion; a means or opportunity of evading a rule, law, etc.: There are a number of loopholes in the tax laws whereby corporations can save money.
1464, from M.E. loupe "opening in a wall" (c.1300), perhaps related to M.Du. lupen "to watch, peer;" + hole. Figurative sense of "outlet, means of escape" is from 1663.