Ratchet
Ratchet may refer to:

Devices
Ratchet (device), a mechanical device that allows movement in only one direction
Ratchet, metonomic name for a socket wrench incorporating a ratcheting device
Ratchet (instrument), a  musical instrument and a warning device

Film and television
Ratchet (Robots), a character in the film Robots
Ratchet, a character in the Widget the World Watcher television series
Ratchet, a character in the Red Lantern Corps DC Comics series
Ratchet (Transformers), a character
Ratchet, one of the Autobot Transformers
Ratchet, a 1986 thriller film by John Johnson

Video games
Ratchet (Ratchet & Clank), a video game character
Ratchet: Deadlocked, a video game

Music
"Ratchet" (Bloc Party song), 2013
Ratchet (Shamir album), 2015
Ratchet, another name for the RnBass genre

Other
Ratchet option, a financial derivative also known as cliquet option
Double Ratchet Algorithm, an algorithm for managing cryptographic keys
Ratchet (slang), a derogatory term
Ratchet Gearloose, a Disney character, paternal grandfather of Gyro Gearloose

See also
Nurse Ratched
Ratched (TV series)