The word "unreckonable" means impossible to calculate or estimate. Antonyms for this word would include "calculable," "countable," "measurable," "quantifiable," "assessable," "predictable," "determinate," "definite," "known," and "understandable." These words all convey a sense of being able to measure, evaluate or understand something, which is the opposite of the idea of being unreckonable. People often use antonyms to help them communicate more clearly or to help them better understand a concept. Having a good grasp of opposite words can help us better understand the nuances of language and use it more effectively in communication.