A jiffy means a very short amount of time, so quick you can barely measure it. When someone says “I'll be back in a jiffy,” they mean they'll return in just a moment. When your dad promises to fix your bike “in a jiffy,” he's saying it won't take long at all.

The word captures that sense of something happening fast, almost instantly. “Hold on a jiffy” means wait just a second. “It'll only take a jiffy” means the task is quick and easy.

Interestingly, scientists sometimes use jiffy as a real unit of time in physics, though it can mean different things. In electronics, a jiffy can mean 1/60th of a second. In physics, it can mean the time it takes light to travel a very short distance. But in everyday conversation, a jiffy just means really, really quick, without anyone measuring exact fractions of seconds.

The word has a light, bouncy feel that matches its meaning. Nobody says “I'll be back in a jiffy” when they're leaving for three hours. It's always about speed, brevity, and getting something done quickly.