noun, plural: centimorgans
A unit of recombination frequency, implying distance along a chromosome.
One centimorgan (cM) is equivalent to a 1% chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossover per generation.
In humans, 1 cM is equivalent to (on average) 1 million base pairs.
Word origin: named after geneticist Thomas Hunt Morgan by his student Alfred Henry Sturtevant.
See also: genetic map.