"Hidden out" is often used to describe something that is concealed or kept secretly out of view. Synonyms for this phrase include "concealed away", "tucked away", "secreted", "shrouded", "veiled", "obscured", "camouflaged", "masked", and "covered up". These terms can be used in various contexts, such as hiding a treasure, concealing a secret, or keeping something private. Using synonyms for "hidden out" can add depth and richness to your writing, so consider using these alternatives to add more variety and interest to your work.