What is “serial monogamy “
Example: You have a wife. She dies. You marry another. She dies. You marry another.
In Mormondom, the Bishops' Handbook
The Lds hierarchy teaches that Lds can be polyandrists [multiple spouses] in eternity -- as long as she was sealed for eternity to each of them when she was serially married to them on earth -- Source: the official church Handbook of Instruction (for Lds bishops), p. 72