In the last couple of years, several web commentators have flinched when Flo, the white-uniformed commercial mascot for Progressive Insurance, described her employer's breadth of coverage as "a most fulsome bounty." The context is a medieval skit with archaic language, so the use of "fulsome" was designed to excite mirth, not to say jollity or hilarity. Yet the word has become an occasion for deadly conflict.
My wife often saw The New York Times use "fulsome" in Flo's sense of "plentiful." Raising my halberd, I sided with the web commentators and my eighth-grade teacher Mr. Hannan, who said no-no-no, it means "excessive" and even disgustingly so, as in "fulsome flattery."
We looked it up in three oldish dictionaries. (We prefer old ones, because new lexicons, not wishing to offend their ignorant purchasers, tend to downgrade etymology and history in favor of contemporary misusage.) The Merriam-Webster fudged, allowing both meanings. The Random House permitted only my definition, not even acknowledging the other.
As usual, the Oxford English Dictionary (I use that huge reference online through my Los Angeles Public Library card) was most helpful. It said both usages date back at least 500 years, the differences possibly arising from confusion between two similar Middle English words, one meaning "full," the other "foul." Over time, dominance has shifted in both directions.
The verdict: "Fulsome" doesn't currently possess any useful meaning, any more than "compromise" or "freedom" does. So don't employ any of these words, or I'll chop your head off.