Definition of "fierily"

The mountain-ash berries across the field stood fierily out from the dark leaves, for a moment.Penguin, 1994, Chapter 2, p. 50

1913, D[avid] H[erbert] Lawrence, Sons and Lovers, London: Duckworth & Co. […]

Her Malay was the Malay of the Staate of Lanchap [...] and she spoke it fierily, with crisp glottal checks, with much bubbling reduplication.

1958, Anthony Burgess, The Enemy in the Blanket (The Malayan Trilogy), published 1972, page 256

Hypnotized, my eyes stared at the small bulge made by that book inside the pocket, they gazed fierily at that one inconspicuous spot as if to burn a hole in the coat.

2006, Stefan Zweig, translated by Anthea Bell, Chess, Penguin