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"
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.
After redlining that bitch, she could barely walk.