Meaning: To improvise that which you are going to say without anything planned.
Author: Shawn Collins, Source: flickr.com, Published under CC BY 2.0 license.
Polish analogue: Wypowiadać się z marszu.
An example of use: The President seems like a very intelligent man when he reads a prepared speech from the teleprompter but he becomes very careless and rude when he speaks off the cuff.