I have never seen the title "lecturer" used in the US. Can you recall where you saw it? The title "instructor" is quite common when the person does not have a PhD.
Lecturer is used at the University of California for instructors with a PhD and no research responsibilities. Some of them even have a form of tenure, "security of employment."
Lecturers are part- or full-time teaching faculty (usually not tenure-track, but some schools like UC's have tenure-track Lecturer tracks) e.g., https://profiles.stanford.edu/48960
Interesting, it was not a title used in the schools I attended (Virginia Tech, William and Mary) or have I seen it used elsewhere. I just checked Harvard, and they use it, too, so it's not just a west coast thing.
