Top Definition
A phenomenon encountered when drinking out of a tall glass with ice that has lodged in the glass, caused by tipping the glass beyond a critical angle to drink, resulting in the ice dislodging and sending a rush of liquid and ice over the drinker's face.
I should have shaken my glass before trying to drink to avoid a Jökulhlaup, but I didn't and now have my drink all over my face and shirt.
by Ryan of the Alleys August 12, 2011

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