1. a slim, graceful woman or girl 2. in the occult philosophy of Paracelsus, a being that has air as its element
This word shows up in the odd little book by Steve Martin, The Pleasure of My Company: “I never have interfered with a relationship, out of respect for the guy as much as for myself, but Brian is a dope and Philipa is a sylph and I am a man, even if that description of myself is qualified by my failure to be able to cross the street at the curb.”