神气 (shénqì) as a noun means 'facial expression, look, manner' — similar to 神情 (shénqíng) but slightly broader, including body language and attitude. As an adjective it has two opposite uses: 'impressive, full of confidence' (positive, like 气派 qìpài) and 'pretentious, putting on airs' (negative). The context and tone decide which meaning is intended.