There is no official definition, in part because there isn't any formal way to define the term that satisfies our intuition.
Most treatments will handle "transpiling" as a special case of "compiling" and some will even handle decompilation as a special case where the object language is higher level than the source. Of course, even defining "higher level" can be quite hard.
Plenty of languages "compile to C" and I see no issue with saying something "compiles to js," especially given that js mostly lacks features of purescript rather than the other way around.