"How did the Defiant's sudden vanishing act seem to other ships?"

A sudden act of some sort that scared you more than the gun.

"Lady Heath's leaving him with us was not a sudden, careless or indifferent act."

She made the news once again for her sudden disappearing act, which none of the local celebrities would dare to do.

This was a hard, sudden and very dangerous act for the enemy fighter on his tail to follow.

It was all so sudden she barely had time to react, much less act in a heroic fashion.

A more sudden act would certainly create suspicion in the Landsraad, hmmm?

You see that we hold all the cards, and we have only to fear some sudden act of violence on their part.

And you are not preparing yourself for that sudden act that will bring a total change.

Who would have thought that Junior was capable of such a sudden, violent act as this?