The phrase "chock-a-block" means completely full, often used to describe a crowded area or overstuffed object. Antonyms for this phrase could include "spacious," "roomy," "empty," "sparse," or "unfilled." These words all suggest the opposite of being completely full or jam-packed. "Spacious" and "roomy" suggest ample space or room to move, while "empty" and "unfilled" indicate there is nothing in the space or object. "Sparse" suggests a small, scattered amount and implies a lack of density, while "chock-a-block" implies a high density. All these antonyms for "chock-a-block" are useful to describe different degrees of fullness, allowing for a more precise description of the surroundings.