Answer
A circle with center $(0,-2)$ and radius $2$
Work Step by Step
Consider $r=-4\sin \theta$
or, $r^2=-4r \sin \theta$
This implies that
$x^2+y^2+4y=0$
This can be re-arranged as:
$x^2+(y+4)^2=16$
Hence, we get the equation of a circle with center $(0,-2)$ and radius $2$
