The word "barrier" defines something that obstructs or hinders progress or entry. Therefore, its antonyms would describe something that allows progress or entry with ease. Such antonyms may include terms like "accessibility," "openness," "advantage," "unrestricted," "freedom," and "welcome." Accessibility describes something that is easily reached. Openness refers to allowing access and communication. Advantage suggests that someone has a favorable position for progress. Unrestricted means no limitations or barriers are present. Freedom denotes an absence of constraints. Lastly, welcome indicates the hospitable reception of something. These antonyms help one understand the opposite of a barrier by highlighting the freedom of movement and ease of progress that lack barriers provide.