Useless MSDS Abbreviations. The terms and abbreviations listed here are confusing, arcane, ambiguous and otherwise useless. We get really annoyed when folks write "N/K" on an MSDS instead of simply stating "Not Known". There is no good reason to abbreviate terms on an MSDS Material Safety Data Sheet! MSDS Relevance: See: MSDS Abbreviations, Useless for some of the more useless abbreviations seen on MSDS's. Beware, the folks that use these may have meant something else