Definition of reindeer moss
: a gray, erect, tufted, and much-branched lichen (Cladonia rangiferina) that forms extensive patches in arctic and north-temperate regions, constitutes a large part of the food of caribou, and is sometimes eaten by humans —called also reindeer lichen
First Known Use of reindeer moss
Seen and Heard
What made you want to look up reindeer moss? Please tell us where you read or heard it (including the quote, if possible).