prereduction
/ˌpriːrɪˈdʌkʃn/noun
1The halving of the chromosome number by the separation of homologous chromosomes at the first of the two divisions of meiosis.
2Separation of the different alleles at a particular heterozygous locus in the first division of meiosis.
3Prior chemical reduction.
Origin
Early 20th century; earliest use found in Proceedings of the Academy of Natural Sciences of Philadelphia. From pre- + reduction, after German Praereduction (E. Korschelt & K. Heider Lehrb. der vergleichenden Entwicklungsgeschichte der wirbellosen Thiere (Allgemeiner Theil) II. vi. 586).