A person who climbs Mount Everest and describes the journey as "a little stroll" is using which literary device?

The individual describing the arduous climb of Mount Everest as "a little stroll" is utilizing understatement, which is a literary device that involves presenting something as being less significant than it actually is. In this case, the severe physical and mental challenges of summiting Mount Everest are downplayed by characterizing it as a simple and casual activity, thus giving the statement a humorous or ironic edge.

Understatement effectively highlights the contrast between the reality of the situation—an incredibly difficult and dangerous endeavor—and the trivial phrasing used to describe it. This device can evoke a sense of irony, engaging the audience by inviting them to consider the disparity between the actual experience of climbing Everest and the nonchalant description given.

In this scenario, the other options do not fit the context of the statement as well. Hyperbole refers to exaggerated claims that are not meant to be taken literally, while simile compares two different things using "like" or "as," and metonymy substitutes the name of one thing for that of another closely associated with it. In contrast, the use of understatement in the description of climbing Everest serves to emphasize the dramatic reality by minimizing it.