Pressure is an effect which occurs when a force is applied on a surface. Pressure is the amount of force acting on a unit area. Pressure is distinct from stress, as the former is the ratio of the component of force normal to a surface to the surface area. Stress is a tensor that relates the vector force to the vector area.
Applicable units are those of quantitykind:ForcePerArea
http://en.wikipedia.org/wiki/Pressure
https://cdd.iec.ch/cdd/iec61987/iec61987.nsf/ListsOfUnitsAllVersions/0112-2---62720%23UAD142
http://dbpedia.org/resource/Pressure
Pressure is an effect which occurs when a force is applied on a surface. Pressure is the amount of force acting on a unit area. Pressure is distinct from stress, as the former is the ratio of the component of force normal to a surface to the surface area. Stress is a tensor that relates the vector force to the vector area.
$p = \frac{dF}{dA}$, where $dF$ is the force component perpendicular to the surface element of area $dA$.
http://www.iso.org/iso/catalogue_detail?csnumber=31889