A topological submersion is a map in Top generalising the sort of map that is called a submersion in Diff.
There are two definitions of a topological submersion $p:Y\to X$:
Each point in $Y$ has a neighbourhood $U$ such that $p{\mid}_{U}:U\simeq p(U)\times Z\to p(U)$ is projection on the first factor. Sometimes $Z$ is required to be a cartesian space ${\mathbb{R}}^{n}$, but this is a bit restrictive.
Each point $p$ of $Y$ has a local section $\sigma :V\to Y$ with $x\in V$ and $p=\sigma (x)$.
The second definition includes the first as a special case.
Surjective topological submersions form a singleton Grothendieck pretopology on Top.