Something topnotch is excellent—it's the highest quality. If you're used to camping, it'll be luxurious to stay in a topnotch hotel.
When you're recommending a movie as one of the best you've seen this year, you might describe it as topnotch. If you're lucky your school's brand new gymnasium will be topnotch, so that your topnotch volleyball team has a great space to practice. The origin of this informal adjective is uncertain, but some experts believe it comes from a 19th-century game.