In thermodynamics, pressure is a quantity of tension whose conjugated extensity is volume, defined as force per unit surface. [1] The basic outline of the concept of "pressure" stems from Swiss physicist and mathematician Daniel Bernoulli, in his 1738 Hydrodynamica, who described pressure of a gas as being due to the bombardment of the particles of the wall of the containing vessel.

Human systems
The translation and understanding of the standard definition of pressure in systems of human molecules is a very difficult subject, as is the case with heat, temperature, and volume. Standard atmospheric barometers, for instance, are not designed or capable of measuring subtle human system pressures, such as to account for phenomena such as variations in territory densities or high school cafeteria seating distributions of alpha-, beta-, and gamma- males and females. [2]

References
1. Perrot, Pierre. (1998). A to Z of Thermodynamics, Oxford: Oxford University Press.
2. (a) Thims, Libb. (2007). Human Chemistry (Volume One), (preview), (ch. 9: "Human Molecular Orbitals", section: Orbtial applications: pgs. 283-295) Morrisville, NC: LuLu.
(b) Thims, Libb. (2006). "Study: High School Cafeteria Seating Distributions", Chicago: IoHT publications.