Vocabulary
words

Error description
This error is thrown in two cases, and the debugger's summary message reflects the cause:

•	A word was executed before being compiled. For example, this can happen if a macro is defined in the same compilation unit where it was used. See Compilation units for a discussion.
•	A word defined with DEFER: was executed. Since this syntax is usually used for mutually-recursive word definitions, executing a deferred word usually indicates a programmer mistake.

Definition

USING: kernel words.private ;

IN: words

: undefined ( -- * )
get-callstack caller undefined-word boa throw ;