1. The property, exhibited by certain gels, of becoming fluid when shaken or otherwise agitated and then becoming semi-solid again at rest or resuming the gel state when standing.
2. In physical chemistry, a structural property that causes certain gels to liquefy when subjected to vibratory forces; such as, ultrasonic waves or even simple shaking, then to solidify again when left standing.
3. The property of certain gels of becoming less viscous when shaken or subjected to shearing forces and returning to the original viscosity upon standing.

Viscosity refers to the property of a fluid or semi-fluid that causes it to resist flowing as a thick and sticky consistency or quality.

4. Etymology: from Greek thigma, thixis, "touch" plus trope, "turning".

Thixotropy literally means, "turning through touch".