from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Slang An occupation or other source of income that requires little effort while yielding considerable profit.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An occupation or any lucrative endeavor that generates considerable income whilst requiring little effort and carrying little risk.
- n. A gorging on luxuries, since someone else foots the bill.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. income obtained with a minimum of effort
The word gravy by itself was used prior to any attestable use of gravy train to characterise 'cushy' situations. It is a shortening of the phrase riding the gravy train, rather than train referring to a number of individuals going the same way or a way of teaching people. (Wiktionary)