The combination of someone with the name Petard, and also happens to be a retard, hence resulting in the term: Petard.
"I can't believe he just did that, what a fucking Petard."
by SnG. April 4, 2010
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a condition of being a complete petard; dumb
Example:

Your friend: My brother suffers from petardism, he’s such an idiot.

You: Omg! that’s crazy
by February 21, 2023
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a condition of being a complete petard; dumb
Example:

Your friend: My brother suffers from petardism, he’s such an idiot.

You: Omg! that’s crazy
by February 21, 2023
Get the petardism mug.