It's So Tricky!

When we were having a discussion( great science word that Jack C!) about pikelets and how they were made up today, we had a vote on whether flour was a solid a liquid or a gas.
None of you children thought it was a solid but you decided it was either a liquid (because it pours) or a gas (because it puffs).
BUT...Flour actually is a sort of solid called a powder. You can probably think of other powders - Baking Soda and Cream of Tartar for example. Below is the tricky answer about why even though it flows it is not a liquid. I think we'll go with the "Would my hand get wet if I put it in some?" question to help us decide.
A liquid flows differently than a powder, because a liquid cannot resist any shear stress and therefore it cannot reside at a tilted angle without flowing (that is, it has zero angle of repose.) A powder on the other hand is a solid, not a liquid, because it may support shear stresses and therefore may display an angle of repose.