"In quietude" is a phrase used to describe a peaceful state of being. However, there are many synonyms that can be used to express the same idea. Some examples include tranquility, serenity, calmness, stillness, peace, quietness, and repose. Each of these words invokes the idea of a peaceful or restful atmosphere. Other synonyms to consider could be harmony, placidity, equanimity, composure, and even bliss. Essentially, any word that invokes a sense of peace, stillness, or tranquility could be used as a synonym for "in quietude".