Which word describes something that is still in existence or not extinct?

The term that describes something still in existence or not extinct is "extant." This word is derived from the Latin "extantem," which means "standing out" or "still existing." It is commonly used in various contexts, such as referring to species that have survived and are not extinct, or to historical documents or works of art that are still available today.

In contrast, the other terms provided do not relate to existence. "Exculpate" refers to the act of clearing someone from blame or fault. "Expedient" typically denotes something that is convenient and practical, often disregarding ethics. "Expiate" means to atone for wrongdoing or to make amends. Therefore, "extant" is the word that accurately captures the idea of being still in existence.