To be vertiginous is to be dizzy and woozy. It's a disorienting feeling.
There's a famous movie called "Vertigo," which is named after a condition of extreme dizziness, often caused by heights. The word vertiginous applies to similar feelings and sensations. The flu makes many people feel vertiginous. Sometimes when you stand up too fast, you can get vertiginous for a second, and most people feel vertiginous after spinning in a circle. Vertigo is a Latin word that originally meant "whirling or spinning," from its root vertere, "to turn."