The 1989 Second Edition of the Oxford English Dictionary will tell you that you’re wrong if your think fulsome means the same as full. If you give a ‘fulsome answer’ to some question (as I’ve noticed many people do), it will tell you that your answer is ‘disgusting, repulsive, odious’, ‘Offensive to good taste’ and ‘gross or excessive’.
Fulsome has had a pejorative meaning since at least the late 14th century. Its original, positive senses meaning, basically, “full, abundant, copious” stopped being used in the early 17th.
Until 2016 that was the record of fulsome in the OED, much to the satisfaction of many a pedant I’m sure. But in that year OED published an update to the entry, which noted that fulsome = full made a fulsome recovery in the twentieth century, with citations for the original sense re-emerging from 1868, and new, even more positive senses coined starting in the 1920s. The older sense has overtaken the newer, such that “in many 20th century examples, it is difficult to be certain whether the older [i.e. middle] critical sense or a neutral or even positive sense is intended.”
This prompted me to have a look at what other meanings recorded in OED fall out of use only to be revived or re-invented centuries later. I rounded up about 8,000 such senses, which OED3 marks with a literal gap in the quotation paragraph.