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When the tip of a recently erect penis peeks over the waistband of underwear, shorts or swim trunks.
I was at the beach and saw Jeanie and got a boner that turned into a periscope. Luckily, no one saw.
by brokenresearch July 11, 2013
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signing on AIM, checking if your stalking target(s) is there, and signing off if she's not, giving the appearance of a periscope breaking the surface and submerging again
It's damn creepy how Ben periscopes for Martina every night after their breakup.
by BMDubbs December 29, 2007
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When the end of an exceptionally long turd sticks straight up out of the water.

Similar to a "breach" (where the turd will arch up out of the water) but fully vertical.

Both of which, really really stink.
Dude, I just totally dropped a periscope in there.
by h.karl February 20, 2010
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When an allen wrench is inserted into an orifice (anus or vagina) and gingerly twisted around, by which the insert-ee can feel sensations that they normally don't feel with an ordinary probe.
My dildo feels great, but that periscope touched me in ways that I've never felt before.
by Fitchio October 08, 2011
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A bit of stem that is poking through a rolled blunt.
That blunt had a huge periscope out the side, but it still smoked just fine.
by Aqib Talib October 05, 2010
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Looking around to cheat on an exam so that your head and neck resemble a periscope. Your head swivels back and forth so quickly that even the dumbest teacher will probably catch you. However, there is always the chance that periscoping works, and it's one of the best feelings in the world. It's commonly used by those too lazy to put any effort into cheating discretely.
John: Dude that test was hard
Fred: Hell yeah, luckily I was able to cheat off the smart kid next to me
John: Ya I could see you cheating from across the room. You looked like a periscope!
Fred: Lol well at least Mr. Walters didn't see! He's oblivious!
by 12chainz February 05, 2014
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