A stylized floral or foliate ornament, often used as a crowning element in Gothic architecture.
A fleuron is an isolated sculpted ornament based on a stylized flower or leaf, often arranged in stages and used to crown or enrich a gable, pinnacle, pediment, finial, or other architectural feature. It is especially characteristic of Gothic architectural sculpture.
Etymology
French fleuron, from fleur, 'flower.'
References
https://www.pierres-info.fr/glossaire_sculpture/index.html | https://www.pierres-info.fr/glossaire/index.html