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1.
When a person reaches age of 30 and feels inclined to take uncontrollable naps throghout the day. may also be linked to urinary incontinence.
I texted hayley ages ago, she must be having a granny nap the old bat.
by Sergeant-bathes-donkeys January 06, 2012
 
2.
An extremely long nap.

Person 1 *wakes up*: Holy crap, I fell asleep.
Person 2: Yeah you fucking did. You've been asleep for 3 hours.
Person 1: Power nap.
Person 2: Mate, that was a granny nap.
by AmyVHS August 28, 2008