renâcler

to display fear, anger or reluctance by snorting (of animals, especially horses); to display reluctance

“Devant l'obstacle, le cheval s'arrêta net en renâclant.” — In front of the obstacle, the horse stopped dead in its tracks with a snort.

Variant (influenced by renifler) of Middle French renaquer, from naquer, from Old French naquier (“sniff”), nascïer (“talk through the nose”).