Rimed snow refers to snowflakes that are partially or completely coated in tiny frozen water droplets called 'rime'.
Rime forms on a snowflake when it passes through a super-cooled cloud.
Snowflakes that are heavily rimed typically produce very heavy and wet snow, with snow to liquid ratios in the 5-1 (i.e. five inches of snow per inch of rain) to 9-1 range.
However, it also allows thicker, and therefore less stable, snow layers to build up.
There has been research into the effect of rimed snow on avalanches.