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View submission: Is sand a liquid???
I think there are other good answers here but to weigh in as well in case another perspective would help. What you're referring to is actually an example of fluidization[1]. This series of articles can help you if you'd like to read more on the subject. However, in short, fluidization is a natural phenomenon that can occur when a solid particulate is exposed to a force from a fluid. You can often see this at science museums, where air will blow through a column and make a powdery substance form unique shapes. This is also what is happening if you were to have flour in your hand and blow on it. The particulate is released into the air, and looks like a "cloud" in that it appears to behave like a gas but is actually behaving more like a suspension.
1: https://www.sciencedirect.com/topics/chemistry/fluidization
However, in a rheological sense, a fluid is characterized as a material that flows when a certain amount of stress is imposed upon it[2]. In terms of phase, a liquid is a type of fluid that is denser than a gaseous fluid and retains some level of bulk molecular structure, in that the individual molecules in a liquid "stick" together but can also slide around if force is applied, which often also factors in some level of surface tension. Sand, in a non-molten state, doesn't do this. There are no significant intermolecular attractive forces that occur between two sand particles. This results in a material that has fluidlike properties, but is not a fluid in the classical sense. Examples of fluids that may surprise you are most gels. For example, poloxamer gels[3] have solid-like properties, and are about the same consistency as hair gel, but will flow when enough shear is applied. Blood[4] is similar to this, in that these fluids have a yield stress.
2: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5811736/
3: https://doi.org/10.1016/j.colsurfa.2021.128246
4: https://www.ahajournals.org/doi/pdf/10.1161/01.res.13.1.48
There's nothing here!