"Sticking like a barnacle" means to be adhering or clinging to something tightly. To describe the opposite, we can use antonyms such as detached, separated, disconnected, free, liberated, unstuck, unattached, and released. These words refer to the release or freedom of something from attachment. For instance, a barnacle can be removed from a surface by being detached or separated from it. Similarly, when we let go of something that is sticking to us, we become free or liberated from its hold. Therefore, by using these antonyms, we can express the opposite of "sticking like a barnacle" in various situations.