What action is described by the term "press down"?

The term "press down" is best described by the word "depress." In this context, to depress means to apply pressure on something, causing it to lower or move downward. This action directly aligns with the idea of pressing down, as both involve exerting force that results in a downward movement or reduction in height of an object.

The other options, while related to pressure or squeezing, have distinct meanings that do not capture the exact action of "press down." For example, "displace" refers to moving something from its original position without necessarily implying a downward movement. "Contract" generally means to decrease in size or shorten, and it does not specifically involve pressing down. "Constrict" involves making something narrower or tighter, often referring to the action of squeezing, but it does not specifically convey the idea of pushing down.

Therefore, the definition of "depress" aligns perfectly with the action described by "press down," making it the correct choice.