That mental note sign you put on something to denote its not well understood and likely to fail at some point. You promptly forget about it and years later a resultant disaster occurs.
the designer had second thoughts about the usefulness of the alarm and made a mental note disasterisk to re-think it. Years later the alarm was ignored and the reactor subsequently blew up.
ayon kay retiredengr ika-16 ng Marso, 2011