reindeer moss

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An erect, grayish, branching lichen (Cladonia rangiferina) of Arctic regions, constituting the chief source of food for reindeer and several other herbivores.

Century Dictionary and Cyclopedia

1. n. A lichen, Cladonia rangiferina, which constitutes almost the sole winter food for the reindeer in high northern latitudes, where it is said to attain sometimes the height of one foot. Its nutritive properties depend chiefly on the gelatinous or starchy matter of which it is largely composed. Its taste is slightly pungent and acrid, and when boiled it forms a jelly possessing nutritive and tonic properties, and is sometimes eaten by man during scarcity of food, being powdered and mixed with flour. See Cladonia and lichen.

Wiktionary

1. n. A lichen, Cladonia rangiferina, that grows in areas of alpine tundra.

GNU Webster's 1913

1. n. (Bot.) a gray branching lichen (Cladonia rangiferina) which forms extensive patches on the ground in arctic and even in north temperature regions. It is the principal food of the Lapland reindeer in winter.

WordNet 3.0

1. n. an erect greyish branching lichen of Arctic and even some north temperate regions constituting the chief food for reindeer and caribou and sometimes being eaten by humans