What's the word ?

Laying on one's side with their head propped up.

Reclining, specifically reclining on his side/elbow.

We don't have a word for that specific pose, but I would describe this individual as "lounging, with one arm propping up their head".

I’m not aware of a single word. If I were to describe this, I’d likely say something like ‘He was laying on his side, with his head propped [up] by his hand.’ The ‘up’ is implicit, which is why I put it in brackets.

Lounging or Laying, Laying isnt really correct but its what I would say off the top of my head.

reclining on one's side sometimes. No single word sadly.

Lethalogica - the inability to bring to mind the word you are looking for

Lying on your side? (I’m not sure either if natives see this please correct me if I’m wrong 😭)

I don't think there is a specific English word for that pose. I think most English speakers would just describe it. He was lying on his side. He was propped on his elbow. If the exact pose doesn't matter, we might say he was lounging, but I don't think that was your question. Adam was lying on his side, propped on his elbow with his head in his hand, staring at the <whatever>.

Obviously the pose has a specific name, I think lounging is a good adjective. However, the facial expression gives me some insight into the emotion that he is experiencing and I would call this “pondering” i.e. in deep thought.

Procrastination lol

Reclining I guess

It's known as "paint me like one of your Fr*nch girls". 

daydreaming?

Apparently the word is recumbent.

Bird. Bird is the word.

I'd say that I was "lying on my side, propped up"

Bird’s the word

Laying on my side with my head propped up? Kinda wordy but that’s how I’d describe it in a book.

I believe "Bird" is the word.

Paint .e like one of your French girl

prop myself up on one elbow?

Pensive

“Doing that” idk either

"Lounging on his side"

Lying

Lateral recumbent

A lot of people are saying “recline” and I just want to point out that “recline” refers to basically any casual way of sitting or laying, like sitting in a recliner chair. “Recline” can work for this, but if someone said the word “recline” I and I think most other native English speakers wouldn’t automatically imagine this.

This might not be entirely correct but I’d call it “lounging”.