It simply means marrying-out, in contrast to endogamy, or marrying-in.
They formerly had endogamy, and it is stated that brothers and sisters married.
endogamy generally exists where the clan life is little developed, and where relatives know and see little of each other.
Sometimes an endogamy of religious origin is met with, among the Jews for example.
What is the relation of endogamy and exogamy (a) to isolation, and (b) to the establishment of a successful stock or race?
There is in this case exogamy in relation to the clan and endogamy in relation to the tribe.
There is no evidence of the practice of endogamy which is so widespread among the Oceanic peoples.
endogamy, en-dog′am-i, n. the custom forbidding a man to marry any woman who is not of his kindred.
Limited exogamy with direct maternal or paternal descent, accordingly, means a reapproach to endogamy.
Natural selection has determined that exogamy produces fitter progeny than endogamy.
endogamy en·dog·a·my (ěn-dŏg'ə-mē)
Reproduction by the fusion of gametes of similar ancestry.
Marriage within a particular group in accordance with custom or law.