Compact usually dark-colored mass of hardened mycelium constituting a vegetative food-storage body in various true fungi

• Detaches when mature and can give rise to new growth

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Sclerotium \Scle*ro"ti*um\, n.; pl. Sclerotia . [NL., fr. Gr. sklhro`s hard.] (Bot.) A hardened body formed by certain fungi, as by the Claviceps purpurea , which produces ergot. (Zo["o]l.) The mature or resting stage of a plasmodium.

Wiktionary Word definitions in Wiktionary
n. A compact mass of hardened mycelium stored with reserve food material that, in some higher fungus such as ergot, becomes detached and remains dormant until a favourable opportunity for growth occurs.

Wikipedia Word definitions in Wikipedia
A sclerotium , plural sclerotia , is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot , sclerotia become detached and remain dormant until ...