Running a piece of equipment, most often an engine or other powerplant, way beyond it's rated maximum, usually in an emergency situation.

Usually, denoted by taking the engine revs or temperature up into the red area on an indicator dial, risking permanent damage or catastrophic failure.

"How fast will that thing go ?"

"One fifty five, but after one forty you'll be redlining"
by Eighth of Seven January 7, 2007
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In broadcasting or sound engineering, redlining is when the levels are set too high and the lines on the screen/board are in the red instead of the more desired orange or yellow. Leaving levels at this high level may cause your audio to sound distorted and unpleasant.
Dude, your levels are up too high, you're redlining!
by nacht_for_haters September 16, 2018
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From redline -
Pronunciation: 'red-'lIn
Function : verb
: redline, to redline, also redlining; to engage in sexual intercourse at an extremely rapid tempo.

Origin in redline : a recommended safety limit; the fastest, farthest, or highest point or degree considered safe.
Hank said he was redlining that bitch for an hour.

After redlining that bitch, she could barely walk.
by Ciao [Scum Crew] April 3, 2006
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when a girl has her period.
no sex tonight, ash is redlining.
by dale'n'ry February 20, 2010
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A set amount of RPMs which your engine can put out before you pretty much blow it up. This is usually where your numbers on your tachometer start turning red, just be sure to keep it out of the red or else $$$$ will be needed. For instance, the redline on my 95 Jeep Grandcherokee is 5,300 RPMS that is exactly where they start turning red, some cars have a rev limiter on them, so due to my rev limiter the engine will not go past 5,300rpms and the engine starts "bouncing" meaning the needle will do the same. I advise you not to try this.
Dude your not supposed to shift while ur racing till you redline it
by Ryan April 7, 2005
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(noun, verb)

An informal sketch over another person's piece of art to point out and correct flaws, especially in anatomy. The sketch is usually in red.
"This piece could really use a redline."

"Could you please redline my drawing of a hand for me, the proportions are off."
by xSilverSky June 29, 2009
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When your car makes a funny noise to tell you that your need to shift gears or the engine will fucking explode
Dudebro: yeah bruh I was redlining in my 2008 camry and the engine blew up what I do my parents are gonna kill me
by ZenMaster69 June 19, 2020
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