a coupling (as in a chain) that has one end that turns on a headed pin
"The swivel connecting the heavy anchor chain to the ship's hull allowed it to rotate freely without twisting."
A piece, such as a ring or hook, attached to another piece by a pin, in such a manner as to permit rotation about the pin as an axis.
"The swivel on the fishing line prevents the rope from twisting around itself during reeling."
In plain English: A swivel is something that can spin around on an axis to change direction easily.
"The old chair had a broken swivel, so I couldn't turn to face him properly."
Usage: Use "swivel" as a noun when referring specifically to a rotating joint like that found on office chairs or door handles, rather than using it for general turning motions which are better described by synonyms such as hinge or pivot. Avoid confusing this term with similar mechanical parts if the object does not actually rotate around an axis.
To swing or turn, as on a pin or pivot.
"The chair swivels smoothly on its central pivot so you can face any direction without standing up."
In plain English: To swivel is to turn something around on a central point so it can spin freely in different directions.
"The chair swivels easily, allowing me to turn and face my friend without standing up."
The word "swivel" comes from the Middle English term swyvel, which was derived from the Old English verb meaning "to revolve." It entered modern usage by combining this root with a common instrumental suffix that denotes an object or tool.