Short for "Not Safe For 56 Kbaud Modems". Tagline abbreviation added to an internet forum post (or other missive) to warn of massive attachment size, which a normal analog phone modem may be incapable of coping with.
by 1Spectre4U December 02, 2003
Not Safe For 56K. A phone line that isn't good enough to get the full connection speed of a 56K modem.
by NSFMR2K December 02, 2003