To avoid, at all cost, any situation that might remotely result in a failure on your, and your liabilities, part.
Example 1:

Stan: "Hey man, let's go to the mall, I want to get something to eat."

Sami: "Nah man, you're only hungry because you have post-high munchies. We should wait at my house before we go out anywhere. Plus, I have some Doritos at home you can munch on."

Stan: "Sweet, failsafe."

Example 2:

Sami: "Hey Charlie, can me and my girlfriend skip school at your house?"

Charlie: "Sure, but you'll have to leave before 12, my mother might come home early for lunch. Gotta be failsafe man."

Sami: "Word!"
by Sami Philadelphia October 6, 2009
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When you can’t maintain erection due to a condom
It was ABOUT to happen but everything went failsafe when she made me jimmy up
by Baldy Solo October 13, 2018
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