There are several antonyms for the word "increscent" which means growing or increasing. The first antonym is "decremental" meaning decreasing or diminishing. Another antonym is "declining" which means becoming less or lower. Similarly, the word "receding" means moving back or reducing in amount. The term "reducing" means making something smaller or lesser. Finally, "shrinking" means becoming smaller or less extensive. These antonyms are often used in contrast to "increscent" in discussions about economic growth, population growth, and other areas where there is a need to describe growth or decline.