Define the term volt.

Hint:Volt is a unit of voltage. When one coulomb current passes through a one ohm resistance then it produces one volt voltage across it. One volt is defined as the electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points.

Complete answer:
Volt is a very ancient unit, it was first defined in 1987 by the 18th General Conference on Weights and Measures but it is used from 1990 and first implemented using Josephson effect for exact frequency to voltage conversion. It is based on the concept of electric potential and potential difference.

Volt is a unit of potential difference between two points. In a conductor, electrons flow only when there is a difference in electric pressure at its ends. If 1 joule work is done to move 1 coumbe of positive charge from one point to another, the potential difference between the two points is said to be 1volt.Hence the unit of volt is in joule of energy per coulomb.Mathematically,
$1V = 1J{C^{ - 1}}$
Also in other words we can say that when a current of one ampere dissipates one watt of power. Hence its SI unit is also based on ${m^2}kg{s^{ - 3}}{A^{ - 1}}$ .

Note:There are various formulas and units of volts but remember in short we can say the potential difference between two points of a conducting wire. An important instrument used to measure the voltage between two positions is a multimeter.