/ ˌæltəʊˈstrɑːtəs; -ˈstreɪtəs; NAmE -toʊˈs-/ noun
[ U , C ] ( alto·stra·ti / -taɪ; NAmE ; -tiː/) ( technical ) a layer of flat clouds lying at medium height, or one of the clouds which form this layer
••
WORD ORIGIN
late 19th cent.: from modern Latin alto- (from Latin altus high) + stratus .