“is” is correct here, due to the implied nouns. “Data” in this case is an appositive and serves to describe the implied noun, “word.” And “plural” is an implied noun for “plural word”
You can see it most clearly if you fill in the implied nouns:
(the word) data is a plural (word)
brbposting@sh.itjust.works 1 year ago
It sure are.
nilclass@discuss.tchncs.de 1 year ago
They sure is!