What action is defined as to honor something greatly?

The action defined as to honor something greatly is best captured by "hallow." To hallow something means to regard it as holy or sacred and to hold it in high esteem. This term often connotes deep respect and veneration, making it a fitting descriptor for honoring something significantly or with great reverence. In various contexts, hallowing can pertain to religious practices, traditions, or even the way we remember and honor historical figures or events.

In contrast, the other options do not align with the definition provided in the question. "Excoriate" refers to criticizing someone severely, which has a negative connotation and is unrelated to honoring. "Gambol" means to run or jump about playfully, emphasizing movement rather than honor. "Expatiate" involves speaking or writing at length or in detail, which pertains more to elaboration than to reverence or honor. Thus, hallow stands out as the only choice that clearly conveys the meaning of greatly honoring something.