While there are wheel spacers that just slide over your studs and lessen the amount of lugnut and stud thread contact, and are very dangerous so don't use them, there are also wheel spacers that bolt on like mine. A wheel adapter adapts your bolt pattern to a different wheel, hence the name. Example: 5x4.5 to 5x5 and such. If it stays the same, in mine case 8 lug to 8 lug, then it isn't adapting anything, its spacing and becomes technically illegal again.
But I still call them adapters at the safety check since they don't know the difference and pass me. Although some tire shops won't touch them because it's against their policy's to touch spacers since if they come loose they are worried about being sued(discount tire)
It was a Jeep thing, but all that stuff broke
92 Jeep YJ Wrangler
"YJ's are for poor people" - Brian