Answer
$y^{2}=-\dfrac {x}{3}$
Work Step by Step
If focus of parabola is $F(p,0)$ this parabola has a horizontal axis
If focus of parabola is $F(0,p)$ this parabola has a vertical axis
In this case parabola has horizontal axis
$y^{2}=4px=4\times \left( -\dfrac {1}{12}\right) \times x=\dfrac {-x}{3}$
