reverse thrust; retrofiring
Technical term in rocketry and aviation for firing engines in the opposite direction to decelerate or change direction.
Use reverse thrust to decelerate during landing.
sudden mental derangement
Obsolete colloquial term for a sudden, extreme change in mental state or behavior, akin to a 'mental U-turn'.
He suddenly went off the rails and quit his job.
Compound of 逆 (reverse) and 噴射 (jet, injection). The colloquial sense is a metaphorical extension of the literal meaning.