The act of defecation, where the person has been waiting for a long time and the result is an inordinately large and powerful session on the crapper. It could possibly break the bowl.
"Jeez Jonny. I just took a thunderdump. They'll hear that in china."

"That thunderdump ruptured something inside I tell ya mate."
by Halit November 5, 2007
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A violent bowel movement, usually loose, which the person may have been storing for some time due to lack of access to ammenities. Propelled by a buildup of gas caused by the fact that a fart during this time would have resulted in a follow through.

It is characterised by shitting out your entire lower colon (and, possibly, a kidney or two) in the space of 2 to 3 seconds.

The result leaves the thunderdumper feeling up to half a stone lighter, noticeably weak, but relieved.
Holy crap, I just had a major thunderdump! That was a three flusher!!
by GatoMuerto September 23, 2011
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A name given to anyone found taking a massive dump in any location, public or private.

Evidence that this person has just used a toilet is a slightly burnt smell resonating from the stall.
God! Help my lungs! Thunderdump Jones was here!!!
by Wooosh51 July 29, 2011
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