Meaning

noun something (a term or expression or concept) that has a reciprocal relation to something else

noun (mathematics) one of a pair of numbers whose product is 1: the reciprocal of 2/3 is 3/2; the multiplicative inverse of 7 is 1/7

noun hybridization involving a pair of crosses that reverse the sexes associated with each genotype

originFrom Latin reciprocus, possibly from a phrase such as reque proque (“back and forth, to and fro”), from re- (“back”), prō (“forwards”) and -que (“and”).

Etymology from Wiktionary, CC BY-SA 3.0