If your story has several unfamiliar terms, such as off-world science fiction or a medical thriller, consider including footnotes or a glossary. Always define such words at first use, a standard procedure in technical writing. This can be done drily, i.e., in parenthesis, or through a combination of dialog and narrative. For example, a character could mention the unfamiliar term, which is described in the following paragraph through the viewpoint of the protagonist. The same advice stands for acronyms.