Define desorption.

Hint: The chemistry of the boundary separating two bulk phases is the surface chemistry. Simply the reverse process of adsorption is desorption. We will mainly focus on the important surface phenomena - adsorption and discuss the term desorption based on adsorption theory.

Complete step by step solution
We know that desorption is the reverse process of adsorption. So, first, we will try to understand adsorption. Adsorption is defined as the surface phenomenon in which particles are adsorbed on the surface of material either solid or liquid which increases the concentration of the species on the material.
We know that desorption is the reverse process of adsorption. So it is defined as the phenomenon where the substance or the adsorbed substance is removed or released from a surface. Simply, it is the process of removing or releasing an adsorbed substance. The adsorption of gases on the metallic surface has been given a particular name, occlusion. The adsorbate can be removed from the surface of the adsorbent. The process of being reversed of adsorption has been rightly named as desorption.

Additional information:
There are some basic terms used in surface chemistry as adsorbate and adsorbent. So, adsorbate is the molecular substance that is adsorbed or accumulated on the surface whereas adsorbent is the substance on the surface of which adsorption occurs. Hence, adsorption is a surface phenomenon. Some examples are charcoal, silica gel, alumina gel, and many more.

Note:
A particle in the bulk of a solid or liquid is attracted equally from all directions and there is no resultant force or unbalanced force on it. During the process, the system is in a state of equilibrium between the bulk phase and an adsorbing surface.