Four kinds of first-cousin marriages are possible. A man could marry (1) his father's brother's daughter (FBD), (2) his mother's brother's daughter (MBD), (3) his father's sister's daughter (FZD), or (4) his mother's sister's daughter[…] 2015 January 4, Bobbi S. Low, Why Sex Matters: A Darwinian Look at Human Behavior - Revised Edition, Princeton University Press, →ISBN, page 63:
(abbreviation, alt-of, countable, initialism, uncountable) Initialism of model-based definition.