valve lash
n.— «If the noise is there whenever the car is running, and not just during acceleration, then it probably is valve tap, more commonly known as “valve lash.”…When you have lash, it means that there’s slop somewhere between the camshaft and the valve train.» —“Make sure tap is not a ping” by Tom Magliozzi, Ray Magliozzi Miami Herald (Florida) Oct. 27, 2005. (source: Double-Tongued Dictionary)