In the sport of roller derby, at the end of a jam, when a player skates back to the bench and can't remember a single thing that just happened on the track. Caused by a combination of nerves, adrenaline, overload of quick, in-the-moment decision-making and whatever you call that thing your brain does where it represses things that are painful.
"WTF just happened out there? I have wicked jamnesia! Who got lead jammer? Why is our jammer in the box? Did I do anything good? Who was my partner? HEELLPPP!?"
A condition in which the excitement of opening a new jar of jam quickly fades, causing the previous ones to be forgotten and left to languish in the back of the fridge. Characterized by the gradual accumulation of half-used jars as novelty outpaces consumption.
jamnesic (adj.) prone to forgetting about old jams hiding in the back of the fridge.
I found three jars of raspberry jam from last year, classic jamnesia.