overdrive

1. (dated, automotive) A gear, on an automobile, higher than the traditional top gear, mainly to allow better fuel economy at highway speeds. In the 21st century, such gears are no longer viewed as "extra" and thus rarely called by this name.Examples: "Near-synonym: top gear"; "In the 1970s, many transmission designs were revised to add an overdrive gear."; "Cruising in overdrive at legal highway speed keeps rpm right at 1800, depending on rear-axle ratio."Synonyms: OD, O/D, O.D.countabledateduncountable

2. (uncountable, figurative) A state of heightened activity.Examples: "overdrive pacing"; "The campaign has been in overdrive since the recent announcement."; "It is true, though it's got nothing to do with me, that the building boom that created the Bombay of my childhood went into overdrive in the years before my birth"Synonyms: top gear, ;, full throttleAntonyms: low gearfigurativelyuncountable

3. (euphemistic, slang) Freewheeling (driving a vehicle with the transmission in neutral) on downhill stretches to achieve higher fuel economy and/or speed than otherwise. In colloquial registers, ethnically bigoted variants have been common, such as Jewish overdrive (alluding to the stereotype of miserly Jews) or Mexican overdrive or Polish overdrive (alluding to stereotypes of foolishness and poverty).Examples: "Of course overdrive is forbidden for dump trucks in the quarry because it is unsafe, but unscrupulous workers were found to be using it because of a perverse incentive involving tonnage piece rates."Synonyms: see at angel gearcountableeuphemisticslanguncountable

4. (engineering, mechanical) A gear ratio higher than 1:1: one in which a single revolution of the driving element corresponds to more than one revolution of the driven element.countableuncountable