The word "muchly" is an informal adverb that means "greatly" or "to a great extent." Its usage is more common in casual or colloquial conversation. Some alternatives to "muchly" include "extremely," "enormously," "tremendously," "vastly," "immensely," and "profoundly." These synonyms convey similar meanings and emphasize the idea of excess or abundance. However, it is essential to remember that using formal language is necessary in professional or academic settings. Therefore, it is wise to use more precise language such as "significantly," "considerably," or "substantially" instead of "muchly".