Passing chord
In harmony, a passing chord is a chord that occurs in a progression that starts with a chord "X" and ends with the same chord "X" but in a different position. It can be used to prolong a harmony.1
A passing tone will almost always occur in the bass, though not always!
You may see the passing chord be called a subordinate harmony.
Examples
Example 1

Example 2
In this case, there are no passing tones between any of the voices.
