A large blanket, usually thick and comfortable, that is used to cover a man as he jerks off. Usually done during the night in private, but can also be done with a companion depending on how big the blanket is. Also, usually the blanket has a white side to it, to better hide the cum on the blanket.
"Man I'm so tired, i think i'm going to go do a quick one in my naked blanket and then pass out"
A special blanket that is only for being naked under. Generally used by couples in the privacy of their own home, but can also be used discretely in pubic settings.
"I'm gonna invite my girlfriend under the Naked Blanket tonight!"