The phrase "most cloistral" implies a sense of isolation or confinement, so antonyms for it would be words that suggest openness or freedom. Some possible opposite words might include expansive, spacious, unenclosed, or liberal. An expansive space suggests room to move and explore, whereas a cloistral space would suggest tight quarters. Similarly, a spacious environment implies plenty of room to spread out and breathe, while a cloistral environment may feel cramped and restrictive. An unenclosed area would lack walls or barriers, allowing easy access and a sense of openness. Finally, the word liberal connotes generosity, openness of mind, and embracing of diverse perspectives, which is clearly the opposite of a cloistered mindset.