An instructor who has been working in the Real World and hasn't just spent four years at a university.

Many school districts allow, and some encourage, the 'lateral' path to teaching because these teachers have relevant experience in the field in which they teach.

Typically, a lateral entry teacher will be given a crash course in education and classroom survival, then allowed to teach for a few years before they're required to get a degree or go back to the Real World.

(Teachers, please note that I'm using the term 'Real World' in its usual anti-teacher sense, but despite my own opinion.)