SLASH is a NetHack variant that adds new player roles, monster types, items and special levels. Its title is a backronym which stands for SuperLotsoAddedStuffHack.
SLASH incorporates many features from earlier NetHack variants, NetHack Plus and NetHack-- (the latter having been developed by the author of SLASH), but also adds entirely new content. There are about 150 new monster types and 8 new player roles (two of them unique to SLASH), new special levels and special rooms, items, weapons, armour and artifacts. Certain game mechanics in SLASH are also different from NetHack, but core gameplay and objectives remain the same.
The original releases of SLASH are based on NetHack 3.1 code. The game was later ported to v3.2, adding the option to use graphical tiles.