noun
A drawing, document, etc. that has been marked for correction or modification.
The maximum speed, temperature, pressure, etc., at which a device (such as the engine in a car, aircraft, etc.) is designed to operate.
verb
To mark a drawing or document for correction or modification.
To operate a device at one or more redlines.
(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.
(audio engineering) To achieve audio levels that will cause clipping (indicated by red in an audio meter).