Lump

Lumps are a type of item used as a base form of all materials without any given shape.

You will generally find lumps of food lying around on the dungeon floor, yet other materials are not unheard of. Also, as every item that was completely destroyed leaves behind a single base item of its main material, you can easily create non-food lumps by blowing up things with a Wand of Fireballs - just do not use stony or wooden items, as these will turn into stones and sticks, respectively. The same goes for killed Golems and selling the lump of gold that was once a gold golem is always a nice addition to your low adventurer salary.

Note that all lumps go under the food tag in your inventory, no matter whether the material itself is edible or not. As all metals and many other non-edible materials have a lump as its base form, you can easily find your food part of inventory full of non-edibles.