Rare but attested; means to place someone/something (or oneself) in a prone position.
Translations
mettre à plat ventreSens médical ou physique : placer quelqu'un ou quelque chose face contre terre. The therapist carefully proned the patient to improve ventilation.
Le thérapeute a soigneusement mis le patient à plat ventre pour améliorer la ventilation.
se mettre à plat ventreUsage plus rare, souvent avec l'idée de se coucher au sol. Definitions
To position (a person or object) so that it is lying flat, especially face downward. The therapist carefully proned the patient to improve ventilation.
To move or lie oneself in a prone position, often with the particle "out." The marine proned out behind the sandbag wall.