1. whirling; spinning; rotary: vertiginous currents of air.
2. affected with vertigo; dizzy.
3. liable or threatening to cause vertigo: a vertiginous climb.
4. apt to change quickly; unstable: a vertiginous economy.
http://dictionary.reference.com/browse/vertiginous
Her luck was extremely vertiginous: one week, she'd get an A on all her tests, and the next she'd break both legs.
