The word annotation feature modifies word definitions to add debugging code. You can restore the old definition by calling reset on the word in question.

Printing messages when a word is called or returns:

watch ( word -- )

watch-vars ( word vars -- )

<WATCH

Timing words:

reset-word-timing ( -- )

add-timing ( word -- )

word-timing. ( -- )

All of the above words are implemented using a single combinator which applies a quotation to a word definition to yield a new definition:

annotate ( word quot -- )