The value with the highest exponent
In a polynomial, the coefficient of the term with the highest degree is called the leading coefficient

- (An example of a leading coefficient)

The Leading Coefficient of the Polynomial - 8x3 + 5x2 + 3x -2  = -8
Which is equivalent to the numerical coefficient 
While a literal coefficient is the coefficient with a letter of the degree of the power

- (An example of a literal coefficient)
The literal coefficient of the term 9x4 = x4

The Degree of a Polynomial is the one with the Literal Coefficient, the degree of the Literal Coefficient, but the leading Degree of the literal Coefficient

- (An example of the Degree of a Polynomial)
The Degree of the Polynomial of the given term - 8x3 + 5x2 + 3x -2  = 3