What is a perfect game of darts called?

A perfect game of 501 darts is typically called a "9 darter" There are several way to hit a 9 darter in 501.

The most typical or traditional way to hit a "nine darter":
Triple 20 (60), Triple 19 (57) and Double 12 (24)
Triple 20 (60), Triple 15 (45) and Double 18 (36)
Triple 17 (51), Triple 18 (54) and Double 18 (36)

Another way is to score 167 with each set of three darts, scoring a perfect 501 total:

treble 20 (60), treble 19 (57) and bullseye (50)