Seesaw (noun)

A long board balanced on a central pivot point, used for play by children, or a similar device or situation in which one side goes up as the other goes down.

Origin:

From the phrase "see-saw" meaning to go up and down.

Examples:

1. The children enjoyed playing on the seesaw in the playground.
2. The stock market has been a seesaw of ups and downs over the past few months.
3. The seesaw of public opinion is likely to swing back and forth.
4. The seesaw of power shifted in favor of the rebels.
5. The seesaw of the water level in the lake is caused by changes in precipitation and evaporation.