How to unmap a var from a Clojure namespace

I was working with a multimethod that I needed to redefine in my REPL and came across this doc.

There is an entry that states if you are in the REPL and need to redefine then you will need to unmap the var because defmulti won't allow you to redef.

This is how:

(ns-unmap *ns* 'something)