The term "be obtainable" is often synonymous with words like achievable, accessible, and reachable. However, there are a number of antonyms to consider when looking for words to describe the opposite of something that is attainable. Some potential antonyms might include unattainable, inaccessible, unachievable, or beyond reach. These words all suggest that something is not possible to achieve or obtain, either due to physical limitations or other uncontrollable factors. Other potential antonyms might include impossible, out of reach, or even undesirable, depending on the context in which the word "be obtainable" is being used. Ultimately, the choice of antonym will depend on the specific situation and what the writer is trying to convey.