Plain English Meaning

The blast of air thrown back by a spinning propeller. It hits the wing right behind the engine and makes that part of the wing produce more lift than the rest of the wing.

Full Definition

The high-velocity column of air pushed rearward by a propeller, which strikes the wing and tail surfaces behind it at a higher speed than the surrounding free airstream. On a multi-engine airplane, the wing area immersed in this faster-moving air produces more lift than the wing area outside it, which becomes important when one engine fails and only one wing is still receiving the accelerated flow.

Context Anchor

Seen in multiengine training when explaining why an airplane becomes harder to control after one engine fails.

Derivation

Slipstream means the stream of air past a moving object. Accelerated means sped up. So an accelerated slipstream is simply the that has been sped up — in this case, by being pulled through the .