The definition of Snuggies™ are made-for-TV products that consist of a blanket with sleeves that is worn as a poncho.(noun)
An example of Snuggies™ are fleece blankets with sleeves that you buy off the TV to keep warm.
Snuggies are long underwear.(noun)
An example of snuggies are long underwear worn to keep warm on cold days.
See snuggies in Webster's New World College Dictionary