false cirrus
nounUK /ˌfɔːls ˈsɪɹəs/ · US /ˌfɔls ˈsɪɹəs/
Etymology From false + cirrus.
1
Climatology, Meteorology, Natural sciences A cloud formation that visually resembles but is not a true cirrus cloud, such as a cloud having high, wispy features due to various atmospheric conditions.