(absolute use of top as adjective: see 27–30). Motoring slang. The top or highest gear; esp. in(to) top (formerly also on (the) top).

= top-gear n. (b).

Engineering. A gear mechanism which may be brought into operation in addition to the ordinary (reducing) gears of a motor vehicle, so that the engine…

An auxiliary speed-reducing gear in a motor vehicle which may be brought into operation in addition to the ordinary gears to provide an…

Of various English words. In form N (without point). Neutral: (a) on an electrical plug, etc. (cf. neutral, adj. 10c); (b) on the selector mechanism…

In a motor vehicle with automatic transmission: the position of the gear selector in which the gears are locked, preventing the vehicle from moving.