To prognosticate is to say what you think will happen later — to put a picture of the future into words. Newspapers, money people, and weather talk do this all the time. The thing they produce is a statement about the future; though actually the English word itself is a verb, not that statement. You prognosticate; the statement is a prognostication. In ordinary talk we just say predict or guess. Prognosticate sounds grander and a bit old-fashioned, as if you were on a stage. A doctor's careful forecast of an illness is usually called a prognosis, a close cousin, not this verb.

預言、預測（較文雅；口語多說 predict）