Which word refers to the act of guessing without sufficient information?

The term that most accurately describes the act of guessing without sufficient information is "conjecture." This word signifies forming an opinion or conclusion based on incomplete information, making it clear that the conclusion is not supported by enough data or evidence.

When someone conjectures, they are essentially making a hypothesis or inference based on what is available to them, without having all the details that would allow for a more informed decision. This aligns closely with the idea of making guesses in the absence of robust evidence.

In contrast, while "speculate" also involves forming theories or conjectures, it can imply a broader range of investigation or consideration than mere guessing. "Theorize" leans more towards developing theories based on more comprehensive analysis, while "assume" suggests taking something for granted or accepting it as true without evidence, but not necessarily involving guessing in a speculative sense like conjecture does. Thus, "conjecture" is the term that best captures the act of arriving at conclusions purely from guessing in an environment of insufficient information.