Periscope

[Britney]

an optical instrument of tubular shape containing an
arrangement of lenses and mirrors (or prisms), allowing a person to
observe a field of view otherwise obstructed, as beyond an obstructing
object or (as in submarines) above the surface of the water.

[Sarah]

signing on AIM, checking if your stalking target(s) is there, and signing off if shes not, giving the appearance of a periscope breaking the surface and submerging again

[Jason Yan]

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.

[Luis Fok]

When the tip of a recently erect penis peeks over the waistband of underwear, shorts or swim trunks.

[Little_Girl]

When you get a b***r in the bathtub, and it looks like the periscope of a submarine

[Couch Potatoe]

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 dont feel with an ordinary probe.

[Couch Potatoe]

A bit of stem that is poking through a rolled blunt.

[Raeanne Dimick]

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 its one of the best feelings in the world. Its commonly used by those too lazy to put any effort into cheating discretely.

[Tina]

The act of agressively fisting a female (or a male) into the vagina or anus hole, then rotating your arm inside the victim left and right, like a periscope, then yanking your arm out.

[Zipporah Schumaker]

a long, vertical tube containing a set of mirrors that gives you a view of what is above you when you look through the bottom of the tube:

[Couch Potatoe]

An apparatus consisting of a tube attached to a set of mirrors or prisms, by which an observer (typically in a submerged submarine or behind a high obstacle) can see things that are otherwise out of sight.