Hell, the term "one-hit wonder" in general is already questionable and debatable, with a lot of music snobs arguing what constitutes a band to be classified as such. Some purists go by chart success, in which case they'll argue that regardless of how ubiquitous and financially successful a band is, they're technically a one-hit wonder simply for only having one Top 10 hit song. Because of this absurd argument, The Grateful Dead, Rage Against the Machine, and KISS are classified as one-hit wonders. Retarded, right?
Then you have people like Todd who get autistic and say, "Um, actually [insert artist] wasn't a one-hit wonder: they had a follow-up song that also charted!", such as Hanson, Rick Astley, and Paper Lace. The latter of which, Todd even acknowledged that they were a two-hit wonder in his video about The Night Chicago Died.
For me personally? I define a one-hit wonder as a band/artist who was unknown at first, then caught lightning in a bottle with a popular song (regardless if it charted), then would fail to recapture their initial success – ultimately being regarded as only creating that one song. In that sense, Modern English's Melt With You fits that description to a T – especially considering the song didn't initially chart. I sure as hell also don't consider Chumbawumba's Tubthumping to be in that category, because their follow-up song Amnesia got a fuck-ton of radio and MTV airplay back when I was young.