What does redline mean?
A redline is a limit beyond which something should not go. On a tachometer or other instrument, it may mark the maximum safe speed, power level, or operating range; the verb can consequently mean running a machine at that limit. In a financial, legal, or editorial context, to redline something is to reject, restrict, or remove it, often in a detailed revision. For example, a lender may redline a mortgage application by reducing the amount it agrees to lend, while an editor may redline a manuscript by marking material for deletion. The term also has a prominent social and historical association with discriminatory housing policies in the United States, where neighborhoods were denied mortgage investment partly because of the race or socioeconomic status of their residents. Thus, the word can describe either a literal performance boundary or a figurative boundary imposed on access and opportunity.
A marked maximum speed, power level, or performance limit on an instrument or machine.
"The engine shrieked as the tachometer needle approached the redline."
Often used in the expression 'hit the redline' or 'reach the redline.'
A threshold beyond which action, credit, approval, or publication is prohibited or requires special review.
"The proposed loan crossed the lender's redline because of its high interest rate."
The figurative sense is especially common in American financial, legal, and editorial contexts.
To reject, restrict, or censor something, especially by refusing credit or approval or by marking material for removal.
"Regulators redlined the proposal, requiring substantial changes before it could proceed."
In US housing contexts, the verb is also associated with discriminatory mortgage-lending practices.
To operate an engine or vehicle at its maximum safe speed or power.
"The driver redlined the engine several times before the car slowed down."
The plural is used for individual limits or lines, especially in automotive, financial, and policy contexts.
"The new safety system alerts drivers before they exceed the engine's redlines."
A redline began as a literal line: on a tachometer, it marks the engine's maximum safe speed.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does redline come from?
The compound combines the color red with the word line, originally referring to a line marked in red on an instrument or document. Its mechanical sense developed from the red line used on gauges to indicate the maximum safe operating level. During the mid-20th century, the expression acquired figurative uses in finance and other regulated fields, and it later became closely associated with discriminatory lending practices in US housing.
Related word forms
How redline is actually used
The technical and automotive senses are common in both British and American English. The credit, housing, and censorship senses are especially associated with US usage; in housing policy, redlining can refer to discriminatory restrictions on lending rather than an individual decision about one application.