Active participial adjectives are formed from the present participles of verbs. They describe nouns that are actively causing or participating in an action.
In quantum mechanics, a tunnelling alpha particle is one
that can escape the nucleus during radioactive decay.
--John Rigden, "J. Robert Oppenheimer: Before the War," Scientific American (modified)
When hybrids mate with pure gray wolves, the resulting offspring appear slightly more wolflike than their parents.[Alternatively: the offspring that result.]
--Robert K. Wayne and John Gittleman, "The Problematic Red Wolf," Scientific American (modified)