Oh, that looks awfully like one of the numerous viruses geraniums can be affected by (I hoped for a nutrient deficiency but fear not). There are no cures and while viruses do not often kill plants (at least in the short term) they will weaken it and render it susceptible to other pests and disease. My advice would be to isolate the plant immediately and, especially if you have other, healthy plants, destroy the infected one(s).

You may like to wait for another opinion here as I am not infallible...but do isolate affected plants and practice the usual plant hygiene