tinea versicolor

noun

tinea ver·​si·​col·​or -ˈvər-si-ˌkəl-ər 

: a common, chronic infection of the skin especially of the trunk and shoulders that is caused by a lipophilic fungus (especially Malassezia furfur and M. globosa), that is marked by the formation of irregular, often scaly patches of discolored skin which may be either lighter or darker than the surrounding skin, and that occurs especially in warm, humid climates

called also pityriasis versicolor