Noun: Particularly bad rolls of dice, a commonly used term when engaged in table-top gaming (and/or gambling).

Named as such for the famously bad rolls of 'Jim'.
"I hit him with two quickened, empowered magic missiles."

(rolls 10d4, gets 10 '1's)

"Oh crimeny, I got a damn Jim Roll. Take... 25 damage."
by Crispy (LS) August 20, 2005
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