The word "anti-alkaline" refers to substances that are acidic or neutral and have a pH lower than 7. To find antonyms for anti-alkaline, we need to look for words that describe substances that are alkaline or basic, with a pH higher than 7. Such words include "alkaline," "basic," "high-pH," "alkalizing," or "nonacidic." These antonyms are used to describe substances that neutralize acids, and they are common in chemistry, health, and agriculture. Examples of alkaline substances are baking soda, soap, and seawater. By understanding the antonyms of "anti-alkaline," we can better understand the properties of substances and their effects on the environment, human health, and other living organisms.