Definition of "redline"

redline

/ˈɹɛd.laɪn/

noun
plural redlines
1. A drawing, document, etc. that has been marked for correction or modification.
2. The maximum speed, temperature, pressure, etc., at which a device (such as the engine in a car, aircraft, etc.) is designed to operate.
verb
third-person singular simple present redlines, present participle redlining, simple past and past participle redlined
1. To mark a drawing or document for correction or modification.
2. To operate a device at one or more redlines.
  1. (automotive) To run an internal combustion engine to its maximum or maximum recommended speed.
3. (Canada, US, urban studies) To deny or complicate access to services (such as banking, insurance, or healthcare) to residents in specific, often racially determined, areas.
  Quotations
  Already ‘redlined’ by profit-hungry telcos, the inhabitants of poor inner city areas can be shut out of the new on-line services through lack of money.
  1995 September, Richard Barbrook, Andy Cameron, “The Californian Ideology”, in Mute‎, volume 1, number 3
4. (audio engineering) To achieve audio levels that will cause clipping (indicated by red in an audio meter).