The word rebound is most commonly defined as to recover after an injury or setback, bounce back up after hitting a surface, or fall in love again after a heartbreak. Its antonyms, on the other hand, refer to the opposite of these actions. The antonym of rebound can be decline, deteriorate, shrink, collapse, or fail to recover. These verbs describe a downward trajectory, loss of progress, or inability to improve or return to one's previous state. Whether it refers to physical or emotional situations, the opposite of rebound is a decline or regression that is unwelcome and can be difficult to overcome.