The definition is:
> For all $N>0$ there is a $\delta > 0$ such that if $0 < \lvert x - a \rvert < \delta$ then $f(x) > N$.
It looks like the limit you have written is the definition of the right-side limit. Note that $0 < \lvert x - a \rvert < \delta$ is equivalent to $-\delta < x-a < \delta$ and $x\
eq a$.