WordNet
pityriasis rosea
n. pityriasis in which an itchy rash develops over the trunk and extremities
Wikipedia
Pityriasis rosea
Pityriasis rosea (also known as pityriasis rosea Gibert) is a skin rash. It is benign but may inflict substantial discomfort in certain cases. Classically, it begins with a single "herald patch" lesion, followed in 1 or 2 weeks by a generalized body rash lasting up to 12 weeks, however usually around 6 - 8.