Appendix A - Review - A.3 Polynomials - A.3 Assess Your Understanding - Page A30: 16

Monomial. The variable is $x$, coefficient is $-4$, and degree is $2$.

The standard form of a monomial is $ax^k$ where, $a$ is the numerical coefficient, $x$ is the variable, and $k$ is the degree of the monomial. Hence, the given expression is a monomial with variable $x$, coefficient of $-4$, and a degree of $2$.