What is "snuggies"

Usage examples of "snuggies".

And what he wants, what he longs for, as he huddles there on the stiff black cushions, drenched through and trembling in the wintry wind, are his old down comforter, his snuggies, his hot water bottle.

Already he has found for him some foot snuggies with the identical pattern of his old ones, a half bottle of his personal French Canadian brand of pine-scented mouth wash, and a pair of spectacles that fit him better than the ones he lost.