Semantics

waist
Он тихо обнял стройный её стан и тихо привлёк её к своему сердцу. [А. Пушкин, Дубровский] He slowly encircled her shapely waist, and slowly drew her to his breast. [A. Pushkin, "Dubrovsky"]
torso
[Он] мгновенно охватил глазами её облечённый в белую кофту и тёмную юбку стройный стан с гибкой и сильной талией. [А. Фадеев, Молодая гвардия] In an instant his eyes captured her well-built, white-sweatered and dark-skirted torso with its lithe, strong waist. [A. Fadeev, The Young Guard]
body
... она повернулась на стуле, легко и естественно изогнула длинный стан, достала с буфета сзади пепельницу... [В. Набоков, Дар] ... she turned in her chair, easily and naturally twisted her long body, obtained an ashtray from the sideboard behind her... [V. Nabokov, The Gift]
This entry is concerned with the use of the word стан to refer to the part of a human torso from the lower ribs to the upper abdomen as an element of the figure or to the upper portion of the torso, e.g. длинный стан "a long waist." This word is used in poetic style to describe the shape of someone's body and also certain gestures and movements involving someone's waist. It does not refer to animals.