Oh, the infinite wisdom of Webster... A Cirro-Cumulus, or Cirrocumulus cloud, is a very specific type of cloud which is found high in the atmosphere and consists entirely of ice crystals. Cirrocumulus clouds are the 'mackerel sky' clouds - those splotchy dotted clouds which seem quite small and fuzzy in the sky. Sometimes they have a wispy trail of snow or ice crystals falling from them.

Oftentimes these clouds are precursors to rain, either due to a tropical system like a hurricane, or due to a imminent front. The name is a combination of Cirrus - high wispy ice crystal clouds], and Cumulus, billowy clouds. Cirrocumulus clouds make for excellent sunsets.