The term "shoutest" is an archaic form of the verb "shout" in its second person singular present indicative form. Some synonyms for "shoutest" that are still in common usage include "yell," "scream," "holler," "bellow," "roar," and "shriek." These words all convey the act of loudly projecting one's voice, often in situations of anger, fear, or excitement. However, each of these words has its own unique nuance and connotation. For example, "yell" and "scream" suggest a higher-pitched quality to the voice, while "bellow" and "roar" convey a deeper, more guttural sound. Ultimately, the choice of synonym will depend on the context of the situation and the desired effect.