What is a comparison without using 'like' or 'as' called?

A comparison without using 'like' or 'as' is called a metaphor. Metaphors directly state that one thing is another, effectively drawing a direct relationship between the two without the qualifiers that a simile uses. For example, saying "Time is a thief" suggests that time, like a thief, can take away moments from our lives, but it does so without explicitly using words like 'like' or 'as.'

In contrast, a simile would use those words to make a comparison, such as "as brave as a lion." An analogy is a more complex comparison that explains one thing in terms of another, often used to clarify or explain an idea; it doesn't fit the definition since it tends to involve more than just a direct statement. Allegory involves telling a story where characters or events symbolize deeper meanings, and while it can contain metaphors, it is not simply a comparison. Therefore, the designation of metaphor is accurate for a straightforward and implicit comparison.