Is there any reliable and fast database architecture that allows to store a dictionary(containing up to hundred thousand words) using mongodb?
For optimal performance, MongoDB schema design must be custom-tailored for each application's unique access patterns. It's better to study general MongoDB design techniques than specific architectures (which may not match your specific application).
Having said that, Wordnik is a great case-study:
Here is how Wordnik apparently modeled their words: source: MongoDB Schema Design