peephole (n.)

• armhole
• beacon
• belvedere
• bleachers
• blowhole
• bridge
• bunghole
• cringle
• deadeye
• eye
• eyelet
• gallery
• gasket
• gazebo
• grandstand
• grommet
• guide
• keyhole
• knothole
• lighthouse
• lookout
• loop
• loophole
• manhole
• observatory
• outlook
• overlook
• pharos
• pigeonhole
• pinhole
• placket
• porthole
• ringside
• spiracle
• tap
• tower
• vent
• venthole
• watchtower