1. What Do You Mean? Jargon used for simplifying text-based interactions between two or more people, used in a way similar to the more popular "lol" "rofl" and "wtf."
2. World Defining Yore-based Machine. A fictional device created by lesser-known author Francine Gaffigan (of Iowa), as a reference and alleged homage to Rube Goldberg, the man behind the concept known as the "Rube Goldberg Device."
The WDYM, in short, was a shopping-mall sized machine which would somehow gather the latent energy in every dream by every man, woman, and child within a 5 mile radius, which would then be used as a cleaner, safer version of more conventional power plants. This energy would then be used to power an exceptionally large virtual game world which would be based partially on the ideas encoded within the captured dream energy.
2. World Defining Yore-based Machine. A fictional device created by lesser-known author Francine Gaffigan (of Iowa), as a reference and alleged homage to Rube Goldberg, the man behind the concept known as the "Rube Goldberg Device."
The WDYM, in short, was a shopping-mall sized machine which would somehow gather the latent energy in every dream by every man, woman, and child within a 5 mile radius, which would then be used as a cleaner, safer version of more conventional power plants. This energy would then be used to power an exceptionally large virtual game world which would be based partially on the ideas encoded within the captured dream energy.
WDYM?
by Xeno-Won November 12, 2010
Get the WDYMmug. by Bro-ena Ravenclaw March 14, 2017
Get the Wdymmug. Wdym?
by Anonymous Anon Girl November 6, 2015
Get the Wdymmug. by YaBishDry November 3, 2015
Get the WDYMmug. “The door is here.”
“Wdym?”
“Wdym?”
by Hey there big boy December 5, 2018
Get the Wdymmug. 
It is just basically a short term of the word what do you mean.
There's also many other words that we can also use it shortly. These words we can also use them when messaging each other instead of just tying the whole sentence which is very long and not cool looking.
More words:
ROFL means Rolling on floor laughing.
STFU means Shut the *freak* up.
LMK means Let me know.
ILY means I love you.
YOLO means You only live once.
SMH means Shaking my head.
LMFAO means Laughing my freaking *a* off.
NVM means Never mind.
There's also many other words that we can also use it shortly. These words we can also use them when messaging each other instead of just tying the whole sentence which is very long and not cool looking.
More words:
ROFL means Rolling on floor laughing.
STFU means Shut the *freak* up.
LMK means Let me know.
ILY means I love you.
YOLO means You only live once.
SMH means Shaking my head.
LMFAO means Laughing my freaking *a* off.
NVM means Never mind.
by III Tempered May 17, 2020
Get the WDYMmug.