Bill, there is this:
from "Greenberg's Guide to Lionel Trains 1901-1942: O and OO Gauges" (2nd edition, 2001) page 38:
"What is an electric-outline locomotive? An electric-outline locomotive is a toy locomotive that is modeled after a real locomotive that gets its power from overhead wire or track for its electric motors.
A steam-outline locomotive, on the other hand, is a toy locomotive that is modeled after a real locomotive that is powered by steam, from hot water heated by burning wood, coal, or oil."
Tinplate and other toy train manufacturers have used different terminology over the years to try to clear up the confusion generated by the fact that we are talking about toy electric trains, but some of these electric trains are electric and some are steam, if you know what I mean...
Using the word "outline" seems to be the term of choice for Greenberg in this reference volume, but other terms have also been used.