The title of Brahmarishi was a status defined and recognized in the sacred Vedas of Vedic religion and Hinduism.
Vishwamitra was the only brahmarishi who rose to the position out of pure tapasya, a journey lasting tens of thousands of years as explained within Hindu mythology.
A Brahmarishi is a perfect example that may be taken from Hindu scriptures to describe the essential unity with Brahman that is necessary for spiritual realization and moksha.