Flour mixed with water produces a suspension, not a solution. The particles of flour are suspended temporarily in a milky-looking slurry. If left sitting long enough, the flour settles to the bottom of the jar.
A solution is defined as a homogeneous mixture of two or more substances. The solute particles are molecular in size. Salt water is an example of a solution. Solutions can be liquid, gaseous or even solid. Metallic bronze is a solution of copper and other metals. A suspension, like flour in water, requires only the mechanical mixing of the solid particles into the liquid, and it is only temporary.