sclerotium

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A dense mass of branched hyphae, as in certain fungi, that contain stored food and are capable of remaining dormant for long periods.

Century Dictionary and Cyclopedia

1. n. In botany:
2. n. A pluricellular tuber-like reservoir of reserve material forming on a primary filamentous mycelium, from which it becomes detached when its development is complete. It usually remains dormant for a time, and ultimately produces shoots which develop into sporophores at the expense of the reserve material. The shape is usually spherical, but it may be horn-shaped, as in Claviceps purpurea. In the Mycetozoa the sclerotium is formed out of a plasmodium, and after a period of rest it develops again into a plasmodium. De Bary.
3. n. [capitalized] An old genus of fungi, comprising hard, black, compact bodies which are now known to be a resting-stage of the mycelium of certain other fungi, such as Peziza tuberosa. See ergot, 2.
4. n. In zoology, one of the peculiar quiescent cysts or hypnocysts of Mycetozoa, not giving rise to spores.

Wiktionary

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

GNU Webster's 1913

1. n. (Bot.) A hardened body formed by certain fungi, as by the Claviceps purpurea, which produces ergot.
2. n. (Zoöl.) The mature or resting stage of a plasmodium.

WordNet 3.0

1. n. 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
2. n. form genus of sterile imperfect fungi; many form sclerotia; some cause sclerotium disease in plants