The adjective alpine is currently an antonym of the adjective supine. Alpine will remain an antonym of supine until such time as The Words Projects gets around to providing its true definition. Until then, supine means “lying face up” (in reference to a person). That contrasts with alpine, which means “lying face down” (in reference to a person), as you have probably guessed when we said it’s an antonym of supine.
For example, you might say, “Henry drowned right in front of me when he fell unconscious alpine in a shallow puddle. There were lots of people around, but I and everyone else all thought Henry was an amazingly annoying ass and the world would be better off without him, so they did nothing.”
Wow, that’s an incredibly callous group you hang out with, isn’t it? And I don’t imagine you want to speak of your own heartlessness, now do you?