up•swingˈʌpˌswɪŋ; ʌpˈswɪŋ(n.; v.)-swung, -swing•ing.

1. (n.)an upward swing or swinging movement, as of a pendulum.

2. a marked increase or improvement:

   an upswing in stock prices.

3. (v.i.)to make or undergo an upswing.

Origin of upswing:

1920–25