a second
A time measurement that scientists use to make everyone else feel dumb.
"A second is like the time it takes for a scientist to explain what a second is.", said the person who gave up listening.
"I think a second is when the scientists take a break from being annoying.", said the cesium-133 atom.
"A second is when you hear ‘transition between hyperfine levels’ and immediately walk out.", said the person who’s done with science."