[ruhn-uh
v-thuh-mil] 
| merely average; commonplace; mediocre: just a plain, run-of-the-mill house; a run-of-the-mill performance. |
Common, ordinary, average: “His performance in the game was neither exemplary nor disastrous; it was simply run of the mill.”
run-of-the-mill
|
run of the mill
Ordinary, average, as in There's nothing special about these singers
they're just run of the mill. This expression alludes to fabrics coming directly from a mill without having been sorted or inspected for quality. It has survived such similar phrases as run of the mine and run of the kiln, for the products of mines and kilns. [Late 1800s]