What is the meaning of Mountain_ash?

A European tree, rowan or, more specifically, European rowan, of species Sorbus aucuparia.

Any of several trees in the genus Sorbus in North America.

A tree native to southeastern Australia, Eucalyptus regnans, the tallest of all flowering plants.

A Texan ash tree of species Fraxinus texensis.

Source: wiktionary.org