noun A piece of metal placed in a horse's mouth and connected to the reins to direct the animal.
A horse hates having a bit put in its mouth.
noun A rotary cutting tool, fitted to a drill, brace, or router, used to bore or drill holes or to remove material from the profile of the workpiece.
router bit
noun Applied to a various small units of currency and coins.
a threepenny bit
noun A coin of a specified value.
a threepenny bit
noun A unit of currency worth one eighth of a dollar, originally of a Spanish dollar but later also US or Canadian; also, a coin with this value, in particular the silver Spanish real.
A quarter is two bits.
noun A coin of a value similar but not equal to this, in particular the 'short bit', i.e. the ten-cent piece or dime.