嶙峋 is a literary descriptive word used to describe jagged, craggy terrain (especially rocks and mountains) as well as a person's physical appearance (bony, emaciated) or moral character (upright, lofty). It appears frequently in formal, written Chinese and in set phrases like 瘦骨嶙峋 (all skin and bones) and 风骨嶙峋 (having a distinguished and upright character). Note that when describing people, the context distinguishes between physical thinness and moral integrity.