Via: Joi Ito's"Yak shaving is the technical term for when you find yourself eight levels deep - and possibly in an recursive loop - in a stack of jobs.". And what do you get when you shave a Yak? Sometimes it Yak's all the way down!
Which is different from "Yak Combing": Which is we someone takes my hair ball writing and makes it presentable, kind of like what Donald Trump's hair stylist must do. Editing with a flamethrower. (or it could involve Yak's)
Update March 7th: Seth Godin warns about shaving, and points to it's possible coinage