An ambiguous word; the meaning depends on the context in which it is used. Primarily used to express an emotion or to fill a void in a conversation.

1. Its conventional meaning can be defined as an exclamation used during times in which a plausible response is non-existent.

2. Also used as a lighthearted response to hearing an unfortunate comment or disappointing news. In this context it is usually something that isn't a particularly a big deal or when it primarily affects someone else; it's sort of a mild schadenfreude.

3. The meaning can be emphasized with the additional of the vowel "o" and therefore changing the sound similar to trombone. "Ploooooop."
4. Onomatopoeic use imitates the sound of feces hitting the toilet bowl during a bowel movement. This is the common form seen on urban dictionary but perhaps not the most pleasant as it is associated with disgusting imagery
5. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect.

Ploop is the sound as well as the action.

Poop, and makes a sound when it hits the water, is ploop. it reflects the sound as well as what it is and what was done.

variation of plop.
a plop that causes water to fly up and smack your ass...leaving you cleansed and refreshed.

the flipping sound your brain makes when you're stoned.

a funny little purple alien and a kick ass word

The lower part of your eyelid.

a cry of exclamation used mainly by that one and only crazy cat lady known as "Znj" upon greeting.

(Znj was last spotted at the crime scene of "Big Daddy Gnomey" running away with a large treasure chest filled with items from the Sanrio store in tow and wearing nothing but a sock monkey hat and a suspicious milk carton shaped body. if you've heard of her whereabouts, please notify Target immediately)