Wiktionary
n. A form of bride exchange in Pakistan and Afghanistan, involving the simultaneous marriage of a pair (brother and sister, uncle and niece, etc.) from each of two households.
Wikipedia
Watta satta , literally give-take, is a form of bride exchange that is common in Pakistan and Afghanistan.
Watta satta involves the simultaneous marriage of a brother-sister pair from two households. In some cases, it involves uncle-niece pairs, or cousin pairs. This form of marriage in Pakistan is typically endogamous, with over 75% marriages involving blood relatives, and 90% of the watta satta marriages occurring within the same village, tribe or clan (jaat, biraderi).
In rural parts of Pakistan, watta satta accounts for over 30% of all marriages. Watta satta is more than just an exchange of women from two families or clans; it establishes the shadow of mutual threat across the marriages. A husband who abuses his wife in this arrangement can expect his brother-in-law to retaliate in-kind against his sister. Watta satta is cited as a cause of low domestic violence in some families, and extreme levels of reciprocal domestic violence in some families of Pakistan.