ratchet
ratch.et \'rach-*t\ n [alter. of earlier rochet, fr. F, alter. of MF rocquet lance head,]of Gmc origin; akin to OHG rocko distaff - more at ROCK 1: a mechanism that consists of a bar or wheel having inclined teeth into w hich a pawl drops so that motion can be imparted to the wheel or bar, governed, or prevented and that is used in a hand tool (as a brace or screwdriver) to allow effective motion in one direction only 2: a pair or detent for holding or propelling a ratchet wheel