the flight of Muhammad from Mecca to Medina in 622 which marked the beginning of the Muslim era; the Muslim calendar begins in that year
source: WordNet 3.0
a journey by a large group to escape from a hostile environment
source: WordNet 3.0
The flight of Mohammed from Mecca, September 13, A. D. 622 (subsequently established as the first year of the Moslem era); hence, any flight or exodus regarded as like that of Mohammed.