What Is A Kiss?

Here are some definitions from scholars in their own fields:

Prof .of Economics:
Kiss is that thing for which the demand is aways higher than the supply.

Prof. of Accountancy:
Kiss is a credit because it is profitable when returned.

Prof. of Algebra:
Kiss is infinity because two divided by nothing.

Prof. of Geometry:
Kiss is the shortest distance between two lips.

Prof. of Physics:
Kiss is the contraction of mouth due to the expansion of the heart.

Prof. of Chemistry:
Kiss is the reaction of the interaction between two hearts.

Prof. of Zoology:
Kiss is the interchange of salivary bacteria.

Prof. of Physiology:
Kiss is the juxtaposition of two orbicularisoris muscles in the state of contraction.

Prof. of Dentistry:
Kiss is infectious and antiseptic.

Prof. of Philosophy:
Kiss is the persecution for the child, ecstasy for the youth and homage for the old.

Prof. of English:
Kiss is a noun that is used as a conjunction, it is more common than proper, it is spoken in the plural and it is applicable to all.

Prof. of Architecture:
Kiss is a process which builds a solid bond between the two dynamic objects

Prof. of Computer Science:
What is a kiss? It seems to be an undefined variable