Jeffing is a thing that can be discussed in mixed company. Apparently it’s a name used for interval training, eg run for 5 minutes, walk for 3 minutes, repeat. It is named for Jeff Galloway who apparently founded* the technique.
* I would have said formalised the technique. I used to tall it lamp posting, in that I’d run to the next lamppost then walk to the next one, but this was when I was a yoof.