Feeling brain-dead, stupid or slow. Where any complex thought makes your brain hurt.

Derived from the feelings of slowness one experiences the day after heavy consumption of alcohol, typically on a Friday. The phrase can be used at any time of slowness though, without alcohol being involved.
Sylvestor: Hey dude, you doing any revision today?
Gerald: Nah man, I've got the Saturday Morgans.
by Fauxy-S February 2, 2011
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