The key words in the definitions that Chris posted are "old-fashioned" and "dated." The majority of people-- even native speakers- under the age of 60 wouldn't understand what you mean to say with "spoon."

Yes. 'Spoon' makes perfect sense here. It means lie together so that the person in front's back is against the stomach of the person behind. It is widely used.

While usually I agree with Jonathan, this time I disagree. My friends and I use the word "spoon" often, to describe lying down on a sofa or a bed with your husband/wife/boyfriend/girlfriend. Usually this is done while watching a movie or tv. Imagine 2 spoons that fit together perfectly. This is the idea.

Hello