A troll mummy is a new type of mummy added in SLASH'EM. Like a regular troll, a troll mummy has a chance of coming back to life after being killed. As their corpse is generated old, eating the corpse yourself is likely to make you sick, and only a pet ghoul or ghast will eat it. The troll mummy is also size huge rather than size large, preventing a pet digester from swallowing the troll and also destroying the corpse.
Troll mummies are rarely too great a threat by the time you encounter them. If you are having trouble with their continued resurrection, eating them is possible - just be prepared to cure sickness. One should remember, of course, that in SLASH'EM unicorn horns must be enchanted to be reliable, although even a +0 unicorn horn is likely to cure the food poisoning in time. Also note that if the corpse is tainted, it will instantly disappear as soon as you start to eat it. It will thus not come back to life while you are eating it, as trolls frequently do.