Jar, n. 1. A rattling, tremulous vibration or shock; a shake; a harsh sound; a discord; as, the jar of a train; the jar of harsh sounds.
2. Clash of interest or opinions; collision; discord; debate; slight disagreement.
And yet his peace is but continual jar. Spenser.
Cease, cease these jars, and rest your minds in peace. Shak.
3. A regular vibration, as of a pendulum.
I love thee not a jar of the clock. Shak.
4. pl. In deep well boring, a device resembling two long chain links, for connecting a percussion drill to the rod or rope which works it, so that the drill is driven down by impact and is jerked loose when jammed.