[ThinkBeat]

I write Lisp but I have no idea what /x means in the example above for instance.

[Jare]

That's a syntax knowledge problem, not a readability problem. \x -> introduces a lambda function with a parameter x, like (x) => in javascript etc.

[dzsekijo]

The "\" (which is "\" rather than "/", as already pointed out) is just an ascii approximation of λ (just like "u" is used to approximate μ).

[kian]

It means a 1-argument lambda, where that one argument is named x