Answer
slope is undefined
Work Step by Step
RECALL:
The slope $m$ of a line is given by the formula $m=\dfrac{y_2-y_1}{x_2-x_1}$ where $(x_1, y_1)$ and $(x_2, y_2)$ are points on the line.
Use the formula above to obtain:
$m=\dfrac{5-0}{-3-(-3)}=\dfrac{5}{0}\space \space\text {undefined}$