What literary device is described as a comparison without using like or as?

A metaphor is a literary device that makes a comparison between two unlike things directly, without the use of the words "like" or "as." This device asserts that one thing is another, thereby creating an implicit association that invites readers to see the first thing in a new light. For example, saying "Time is a thief" suggests that time can stealthily take away our moments just as a thief might steal valuables, enhancing understanding of time's elusive nature.

In contrast, a simile explicitly uses "like" or "as" to make a comparison, such as "Her smile was like sunshine." An analogy draws a more extensive connection between two things, often explaining one thing in terms of another, which is not as succinct as a metaphor. An allegory, on the other hand, is a narrative that conveys a deeper moral or political meaning, often through symbolic figures and actions, rather than focusing on brief direct comparisons. Therefore, the definition given in the question aligns perfectly with the characteristics of a metaphor.