Today I come across a word I hadn't seen before disinflation.

This term refers to a slowing of the rate of change of inflation over time.

Note that this term refers to a rate of change as this quantity is the first derivative of inflation vs time. This means it's possible to both be in an inflationary and disinflation phase at the same time, but this can only be temporary as a decreasing rate of inflation will eventually hit zero at some point.

I wouldn't be surprised if this term was highly confusing for a lot of people, I certainly found it a bit odd.