(n.) A hole, or crevice, through which one may peep without being discovered.

Texas tower air hole armhole beacon belvedere bleachers blowhole bridge bullet-hole bunghole conning tower cringle deadeye eye eyelet gallery gasket gazebo grandstand grommet guide keyhole knothole lighthouse lookout loop loophole manhole mousehole observation post observatory outlook overlook peanut gallery pharos pigeonhole pinhole placket placket hole porthole punch-hole ringside ringside seat sighthole spiracle tap top gallery tower vent venthole watchtower