The correct answer is- 'Seasoned' Key Points - let's look at the meaning of the given word and the correct answer. - Childish(adjective): If an adult is childish, they behave badly in a way that would be expected of a child. - Example: He wasn't enjoying the occasion so he thought he'd spoil it for everyone else - it was very childish of him. - Seasoned(adjective): having a lot of experience of doing something and therefore knowing how to do it well. - Example: a seasoned campaigner for human rights. Hence, the word Seasoned is the most appropriate antonym for Childish.