Sliming is the process of a character turning into green slime as the result of either the slime's touch attack, using a biting attack against the slime, engulfing it or eating a glob of it. It is shown as Slime in the status line. The process is fatal for you, but for other monsters they simply turn into a green slime. It is a slow process - you will have nine turns to take action against it if it is induced by the slime's attack or biting it and four turns if by means of engulfing it.
For more information, see the main article on sliming.
Note that the in-code description for green slime includes provision for a 0d0 sliming passive attack, but that as of 3.6.0, this has not been implemented. However, the sliming passive attack still contributes to the experience points you earn for killing the green slime.
Yet another monster borrowed from Dungeons & Dragons.
In slashem, the green slime's attack has 1/4 chance of succeeding instead of 100%. Here, they also drop normal corpses instead of globs (still unsafe to eat).