snowflake
From Glossary of Meteorology
Colloquially an ice crystal, or more commonly an aggregation of many crystals that falls from a cloud.
Simple snowflakes (single crystals) exhibit beautiful variety of form, but the symmetrical shapes reproduced so often in photomicrographs are not found frequently in snowfalls. Broken single crystals, fragments, or clusters of such elements are much more typical of actual snow. Snowflakes made up of clusters of crystals (many thousand or more) or crystal fragments may grow as large as three to four inches in diameter, often building themselves into hollow cones falling point downward. In extremely still air, flakes with diameters as large as 10 inches have been reported.
