what is a list designator?

Hi,

The hyperdoc for the case macro talks about list designators.
But what is a list designator? Reading the definition in the hyperspec did not help.

I guess I understand what is a string designator: a keyword, a symbol or a string.
But a list designator? The case examples seem to indicate that even a number is a list designator.
I am puzzled.

In the glossary is written that with a non-nil atom is dealed like with a singleton (a list of one element). Thereunto if you want to use t or otherwise as a normal-clause you must use the singleton.

Thanks, I looked at the section 1.4.1.5 on designators, but the info is indeed in the glossary.