A female calf that is born as a twin with a male calf and is sterile because of hormonal exposure during development in the womb.
From 'free' (meaning barren or unproductive) + 'martin' (possibly from Saint Martin or an old term for female animals). A specialized agricultural and veterinary term dating to at least the 1700s.
Freemartins taught scientists about how powerful hormones are in development—the male twin's testosterone prevents the female from developing normal reproductive organs, which was groundbreaking evidence that hormones shape bodies.
Complete word intelligence in one call. Free tier — 50 lookups/day.