Load up is a term used by casino players that refers to someone playing with the highest stake the game allows.
For example, in video slots, players are often limited by the software when it comes to how much they can bet. Furthermore, the highest bet is sometimes a correlation between the amount of money you’re betting and the number of coins you’re betting per line. If a player is betting the highest number of coins and the highest amount, they are loading up or playing with load up bets.
While it can be used in various games, the term is normally used by those playing slot machines in land-based casinos or video slots in online casinos. Still, keep in mind that some players might use it when talking about other casino games too. In both cases, the term has the same meaning.