Q:

How to list the current set of words in Forth

Is it possible to get the list of all words which are currently defined in Forth (for example in Gforth)? 

A:

Standard WORDS word prints all the words from the top vocabulary (wordlist) only — see the specification .
TRAVERSE-WORDLIST proposal defines API to enumerate words in given wordlist. Some Forth-systems already implemented this proposal ([update] it is already in the draft).
Although there is no standard API to enumerate all defined wordlists. GET-ORDER gives a list of the context wordlists only (i.e. wordlists in the scope).
Some Forth-systems have VOCS word that prints all defined vocabularies.
Other possible APIs are specific for particular Forth-system. For example, SP-Forth has ENUM-VOCS word to enumerate all known wordlists.

