1. The powdery solid residue from combustion of coal, peat, wood, etc.

2. (volcanic ash) Mineral particles smaller than 2 mm that are ejected in large quantities by explosive volcanic eruptions. Such eruptions occur when volatile compounds expand violently as they approach the surface, ejecting magmatic rock as foam that condenses as it cools.

3. One of 63 species (genus Fraxinus) of trees that occur throughout temperate regions of the northern hemisphere. Many are grown for their timber or for ornament.