before dawn or daylight
• (a.) Held or being before light; -- a word applied to assemblies of Christians, in ancient times of persecution, held before light in the morning.
An`te·lu'can adjective [ Latin antelucanus ; ante + lux light.] Held or being before light; -- a word applied to assemblies of Christians, in ancient times of persecution, held before light in the morning. ' Antelucan worship.' De Quincey. 
antelucan 1. Being before light; a word applied to assemblies of Christians, in ancient times of persecution. 2. Held before light in the morning.