1. all of a sudden - Adverb
2. all of a sudden - Phrase
without warning
happening unexpectedly
Source: WordNetI was sitting in a chair in the patent office at Bern when all of a sudden a thought occurred to me: "If a person falls freely he will not feel his own weight." I was startled. This simple thought made a deep impression on me. It impelled me toward a theory of gravitation. Albert Einstein
There is a thing that happens when you are not as privileged and you start hanging out with a seedier crowd because you can afford to do the same things, And all of a sudden the big night out is sitting in somebody's trailer, smoking something or getting hold of something to put up to your nose. Eddie Vedder
It's a weird scene. You win a few baseball games and all of a sudden you're surrounded by reporters and TV men with cameras asking you about Vietnam and race relations. Vida Blue
That's the way things come clear. All of a sudden. And then you realize how obvious they've been all along. Madeleine L'Engle
I was very much into buying contemporary art, but I've just decided I want to get rid of it all. Not that it's not great art, but all of a sudden my mood has changed, and I want to go back to seventeenth- and eighteenth-century masters. Sylvester Stallone
When someone's wealth improves, all of a sudden their house's columns appear to be crooked. Armenian Proverb