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1.
A person that acts completely retarded when exposed to water.
"Don't let Brian go swimming. He's a total Aquitard."
by wxcoder85 December 07, 2009
 
2.
An aquitard is an underground layer of something else that does not allow water to flow through it.
An aquitard is clay or really solid rock that is nonpermeable.
by Tiger128 May 07, 2009
 
3.
The inability to function on a physical, mental and emotional level when exposed to water.

Originated from the hydrological definition of an underground aquifer no longer able to retrieve water.
Causations: Belly-flop, exhaustion, concussion, swimming into a yellow plume, discovering a brown smear on your chest, falling off the inflatable donut etc.
"So how did the kids go at the swimming finals?"
"Well Shayne did pretty good, but Dayna was a bit of an aquitard"
by Dodgy Rhino April 06, 2013
 
4.
A person generaly mentally unstable that claims to be a famous mermaid but in reality is just a fiend intemperance of the human imagination. Is extremely in denial of not being a goddess.
Ilana: Im Ariel and a mermaid!
Everyone: No your just an aquitard
by Monkeysandpoo1 February 08, 2012