When someone is irate, they are extremely angry — not a little cross, but really burning. People often use the word when the anger comes from feeling treated in an unfair way: a shop that will not take something back, a bill that looks wrong, a flight that is cancelled with no help. You will meet it more in newspapers and careful writing than in everyday talk. A headline might say “irate passengers” or “an irate letter.” In the street, the same person would more likely say they were furious, or just very angry. It is an adjective: an irate customer, an irate parent. You cannot say “I irate” — that is the wrong shape. Though actually, it sits a little above ordinary angry: it sounds formal, almost like a label the writer puts on a crowd.