We don't have synonyms for mossier yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are dossier, messier and mosser.
(n) :
(UK, Australia, New Zealand, colloquial) Alternative form of mossie (“mosquito”). [(South Africa) Any of various species of sparrow, especially Passer melanurus.]
(n) :
(UK, Australia, New Zealand, colloquial) Alternative form of mossie (“mosquito”). [(South Africa) Any of various species of sparrow, especially Passer melanurus.]