覗う[ukagau] to peep (through)
覗き[nozoki] peeping
覗き見[nozokimi] peeking
覗きこむ[nozokikomu] to look into
覗く[nozoku] to peek (though a keyhole, gap, etc.)

覗魔[nozokima] peeping tom
管の穴から天を覗く[kudanoanakaratenwonozoku] Have a narrow view of things
覗眼鏡[nozokimegane] peep show
覗機関[nozokikarakuri] peep show
差覗く[sashinozoku] to peek