There are a variety of synonyms for the word "gassed-up" that can be used in different contexts. Some common synonyms include "filled up," "topped off," "refueled," or simply "filled." These words can be used interchangeably depending on the type of fuel being used, such as gas or diesel. Other synonyms for "gassed-up" that convey a similar meaning but with a different connotation include "powered," "energized," or "revved up," which may be used in the context of a vehicle or machinery. Additionally, in slang terms, "gassed-up" can mean to be intoxicated, so synonyms such as "drunk" or "buzzed" may also be used in this context.