The definition of frass is the waste left as an animal's bowel movement.
An example of frass is what a bug excretes after eating a leaf.
the mixture of fecal material and plant matter left by an animal, esp. an insect, after it has eaten its way into a tree, plant, etc.
Origin of frassGerman ; from fressen, to devour: see fret
Debris or excrement produced by insects.
Origin of frassGerman, feed, result of eating, insect damage, from Middle High German vrâz, from Old High German fraz, from frezzan, to eat; see ed- in Indo-European roots.