Answer
not a monomial
Work Step by Step
RECALL:
(1) A monomial is a product of a constant and some variable/s whose exponents are nonnegative integers.
(2) The degree of a monomial is the sum of the exponents of its variables.
Using the rule $\dfrac{1}{a^m} = a^{-m}$, the given expression is equivalent to:
$=-2x^2 \cdot \frac{1}{y^3}
\\=-2x^2 \cdot y^{-3}
\\=-2x^2y^{-3}$
The exponent of $y$ is $-3$, which is not a nonnegative integer.
Thus, the given expression is NOT a monomial.