A thudder is an enormous cock! Generally dressed to the side and causes problems when wearing anything shorter than knee length.

Its called the "Thudder" due to the noise it makes when it hits a hard surface (which due to its size is very often)
Ben and Mike standing at the Urinals (Ben is sneaking a look at Mikes cock

Ben: Hey Mike look at the size of my cock
Mike : zzzzzip, "THUD" *splash*
Ben: Oh thats why they call it the thudder

Mike then wakes up and realises the thudder dream needs to be let go!
by Let_Me_Go June 10, 2011
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British slang - a really heavy or massive cock or club dick, one that hits you with a deep "Thud" when it falls on your head or arm.
My boyfreind dropped his huge thudder on my face last night ... it slapped me like a rubber club, but I loved it !
by Word-Wizzard January 28, 2012
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noun. Object that has large or massive properties
That nugget of danks i got was a THUDDER
by BigFatPaulE March 14, 2009
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a penis of such prodigious weight that it makes a "thud" sound when brought out and down.
I was surprised that for a man with such a light frame he produced quite a thudder.
by nanode August 24, 2009
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noun . a portable container made of tin used to hold alcoholic beverage, (see: can) which is still more than half full of the chosen beverage due to the lack of drinking ability of its holder. It is common practice in certain areas that punishment is imposed on the owner of the said 'thudder' usually drink such beverages the morning after the night before!
Kevin cannot drink for shit and is known to leave the occasional thudder beside my sofa and fall asleep with his tongue out
by El Monzo March 15, 2007
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