1. a mechanical device with a toothed wheel that allows motion in only one direction
2. a tool with a ratcheting mechanism, especially a socket wrench

1. to move or cause to move by degrees in a particular direction, typically making the process irreversible

Examples

• The mechanic used a ratchet to tighten the bolts.
• The parking brake uses a ratchet mechanism to stay engaged.
• Tensions continued to ratchet up between the two countries.
• The company decided to ratchet down its spending.
• He grabbed his ratchet set from the toolbox.
• The ratchet clicked as she turned the handle.
• Political rhetoric tends to ratchet upward during election season.