In plain English:

`search_entry_hashed` is a parametric function. It works in a type safe way on any kind of K and V. It takes as arguments a reference to a mutable hash table, a hash function and a key, and returns an `Entry` object whose precise type depends on the type of the parameters.

You could hardly express that more succinctly. You can't understand it by skimming it, but it is a complex definition.