"Gen up" is a phrase that means to learn or study something thoroughly. There are a number of synonyms that could be used in its place, including "bone up," "cram," "study," "research," and "familiarize oneself with." Other synonyms could include "review," "peruse," "examine," "scrutinize," "analyze," and "delve into." In essence, any phrase or word that implies a deep understanding of a subject could be used as a synonym for "gen up." Whether it is for school, work, or personal interest, it is important to know these synonyms in order to better understand how to consume and process information effectively.