disciple of Buddha; Buddhist
Refers to a follower or disciple of the Buddha, often used in Buddhist contexts. Sense 2 is essentially the same as sense 1, just phrased differently.
He is known as a devout disciple of Buddha.
The disciples of Buddha traveled to spread the teachings.
仏教徒 means a Buddhist in general, whereas 仏弟子 emphasizes being a direct disciple or follower of the Buddha.
Compound of 仏 (Buddha) and 弟子 (disciple). The reading ぶつでし follows standard on'yomi for 仏 and kun'yomi for 弟子.