Thixotropic solids have a thick and gelatinous form yet become more liquid upon activity. Many examples are found in the home: ketchup, mayonnaise, toothpaste, for example. This is a distinct state of being beyond gelatinous.
I had been groping for this word some time ago and was pleasantly reminded of it by the Last Word question, What’s the best way of getting ketchup out of the bottle without breaking the bottle or splattering the sauce?