acervulus acervulus /ˌæsərˈvjuːləs/

noun

1. Small asexual fruiting body resembling a cushion or blister consisting of a mat of hyphae that is produced on a host by some fungi  ( acervulus )
   small asexual fruiting body resembling a cushion or blister consisting of a mat of hyphae that is produced on a host by some fungi