Definition:Nowhere Dense/Definition 2

Definition
Let $T = \left({S, \tau}\right)$ be a topological space.

Let $H \subseteq S$.

$H$ is nowhere dense in $T$ :
 * $H^-$ contains no open set of $T$ which is non-empty

where $H^-$ denotes the closure of $H$.

Also see

 * Equivalence of Definitions of Nowhere Dense