I stand corrected, per @ucbalumnus, but it is indeed a matter of semantics. My son’s favorite teacher thus far, is indeed a Full Time Lecturer, and he makes that well known if ever addressed as Professor (sort of like a Master Sargent being called Sir :D). He does though have a PhD in Mechanical Engineering. What you won’t find are graduate students teaching any facet of the undergraduate curriculum, with the exception of voluntary tutoring sessions. Compare that to Berkeley where they typically have 60+ TAs in Mechanical Engineering alone (that’s not to pick on UCB, all big research institutions are the same, it’s just the one that I had the stats from via ASEE).