An unwritten law dictating that if a food or other consumable item is dropped onto the floor, it may be picked up up and eaten within five seconds. The reasoning behind this is that dirt and germs take six seconds to transfer from one surface to another.
"Oops, dropped my popsicle. Five second rule!"
(Proceeds to pick up dirty-ass rocket pop and suck the lint off of it)
After you break up with someone, you are not allowed to mourn over the loss for more than 5% of your time being with them.
The 5 percent rule goes like this: you can mourn over the loss of a boyfriend or girlfriend for no more of 5% iof the time being together (as previously stated). FOR EXAMPLE, if you dated someone for 60 minutes, you can mourn over your tragic loss for 3 minutes (if i did my math correctly)
The rule by which one determines whether or not food is safe after falling onto the floor. That is, if you are able to retrieve said item within 5 seconds, it is not dirty and is safe to eat.
* Note: in fraternity houses, this rule is the 1.5 second rule. Rule is invalid in the restroom.
Person 1: Oh no, my chicken wing fell on the floor!
Person 2: 5 ... 4 ... 3 ... 2 ...
Person 1: Got it!
Person 2: 5-second rule. It's yours, dude.
"Man, she went off like Mount St. Helens!" = Acceptable within the 21.5 year rule. Mount St. Helens tragedy was in 1980, well over 21.5 years ago.
"Man, she freaked out like the people on the planes right before they slammed into the towers!" = Unacceptable within the 21.5 year rule. Will become acceptable on March 11, 2023.