peephole
noun
[ ˈpiːphəʊl ]
• a small hole that may be looked through, especially one in a door through which callers may be identified before the door is opened.
• "she peered through the security peephole in the solid oak door"
Similar:
opening,
gap,
cleft,
slit,
crack,
chink,
keyhole,
aperture,
orifice,
crevice,
cranny,
fissure,
spyhole,
arrow slit,
embrasure,
squint,
judas (hole),
