English An adult ash borer. Noun ash borer (plural ash borers) A moth (Podosesia syringae) in the clearwing moth family (Sesiidae). Synonyms lilac borer Derived terms emerald ash borer Further reading ash borer on Wikipedia.Wikipedia Podosesia on Wikispecies.Wikispecies Podosesia syringae on Wikimedia Commons.Wikimedia Commons Wikiwand - on Seamless Wikipedia browsing. On steroids.