Dilatant fluids increase their viscosity with agitation. We all know that with agitation, cream becomes butter. Candy compounds, clay slurries and similar heavily filled liquids do the same thing. Plastic fluids have a yield value which must be exceeded before flow will start. From that point on the viscosity will decrease with an increase in agitation.
Tomato catsup is the best example of such a product.
Pseudo-plastic fluids show a decrease in viscosity with an increase in agitation, but they do not have a yield value. Many emulsions fall into this category. Thixotrophic fluids exhibit a decreasing viscosity with an increase in agitation, although the viscosity at any particular rate of motion may depend upon the previous agitation of the liquid. The Saybolt Furol version is for high viscosity liquids. A measured volume of liquid is allowed to flow through an orifice of specified dimensions and the time that it took to get through is measured in seconds.