Also found in: Acronyms.
The highest level of function, operation, or performance that someone or something can achieve. It's been hard-fought game, and the team is going to have to go into fourth gear if they want to force overtime. You guys need to get into fourth gear creatively if you want to break into such a highly competitive market.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.