空からぶかし

noun

engine idling; revving in neutral

Refers to running an engine without engaging the transmission, often with the accelerator pressed. Common in automotive contexts.

• 信しん号ごう待まちで空からぶかしをするのは近きん所じょ迷めい惑わくだ。

  Revving the engine while waiting at a traffic light bothers the neighbors.

• エンジンの空からぶかしは燃ねん費ぴを悪わるくする。

  Idling the engine worsens fuel efficiency.