A straightaway is a straight section of a road or racetrack, where there are no curves or turns. On a NASCAR track, the straightaways are where drivers can really accelerate and reach top speeds before they have to slow down for the corners. If you've ever ridden a bike around a path with lots of twists and turns, you know how good it feels to finally hit a straightaway where you can really go fast without worrying about steering.

The word also means immediately or right away. If your teacher says “come here straightaway,” she means right now, not in five minutes. When something needs to happen straightaway, there's no time to waste or delay. You might tell your little brother, “clean up your mess straightaway,” if you need the table cleared before dinner starts.

Notice how both meanings share the idea of directness: either a direct path without curves, or direct action without delay. In both cases, there's nothing in the way to slow things down or change direction.