To partition something or a portion of something with a section or other barrier to make it private or obscure it from view. A noun or pronoun can be used between "section" and "off." To save money, Chris moved into the living room and sectioned off a space for his bed with an old bedsheet tacked up to the walls and ceiling. They've had to section the movie set off with a giant makeshift fence so that onlookers don't learn any secrets about the film.