break-even point: n. in the process of implementing a new computer language,

:break-even point: n. in the process of implementing a new computer
language, the point at which the language is sufficiently effective
that one can implement the language in itself. That is, for a new
language called, hypothetically, FOOGOL, one has reached break-even
when one can write a demonstration compiler for FOOGOL in FOOGOL,
discard the original implementation language, and thereafter use
working versions of FOOGOL to develop newer ones. This is an
important milestone; see {MFTL}.

[Since this entry was first written, several correspondents have
reported that there actually was a compiler for a tiny Algol-like
language called Foogol floating around on various {vaxen} in the
early and mid-1980s. The above example may not, after all, be
hypothetical. -- ESR]
-- The AI Hackers Dictionary