Cirrocumulus lacunosus

Description
Cirrocumulus lacunosus, also known as Cirrocumulus lacunar or Cirrocumulus lacunaris, is a variety of cirrocumulus cloud. The term lacunosus is from Latin, meaning "full of hollows".

Cirrocumulus lacunosus is a relatively rare cloud form that occurs as a cloud layer with circular gaps or holes in it. Formation is commonly attributed to a cool layer of air mixing with an overlying, warmer atmospheric layer, with each downflow of air creating an individual gap. These gaps normally have frayed edges, and are often arranged in a manner that resembles a net or a honeycomb.

Similar cloud forms
Lacunosus must not be confused with the superficially similar cloud form cavum, a supplementary cloud feature also known as a fallstreak hole or as a hole punch. A fallstreak hole usually consists of one very large hole in a cloud layer combined with visible downdraft filaments in the centre, as opposed to 'lacunosus', which consists of a compact lattice or honeycomb of small to tiny holes.