بَيَاتٌ
1.
A coming upon the enemy by night; (Mgh;) a sudden attack upon, and conflict with, the enemy by night; (Msb;) a great slaughter (S, M) among the enemy, (S,) or a people, (M,) and vehement conflict with them; (S, M;) a coming upon people in the night, and making a sudden attack upon them, while they are heedless; (T;) an attack upon a people by night; a going to the enemy in the night, without their knowledge, and taking them by surprise: (TA:) a subst. from 2; (S, M, Mgh, Msb;) like سَلَامٌ from سَلَّمَ. (Mgh.)
2.
أَتَاهُمُ الأَمْرُ بَيَاتًا
The thing, or event, happened, or came, to them in the latter part of the night. (T.)