If you splash out, it means that you spend a lot of money on something that you don't necessarily need.
I was feeling down, so I splashed out on a new computer and then felt great.
The shops were full of people splashing out after pay day.
I fancy sushi. Let's splash out and go to that new restaurant down the road. It's expensive but the food looks delicious.
Don't confuse it with
If someone makes a splash it means they suddenly become very successful or famous.
Bradley Wiggins made a splash by winning the Tour de France. Nobody had heard of him and a week later he started the Olympic Opening Ceremony.
When Cao Yuan and Zhang Yanquan won gold in the diving final, they dashed the hopes of British competitors Tom Daley and Pete Waterfield. The local pair had led the competition in the first three rounds but suffered as a result of a poor fourth dive.