In linguistics, “gender” is even more complicated than that. A “gender” is a category of nouns and adjectives that share a distinctive morphology. The masculine/feminine/neuter breakdown that we find in Romance languages correlates to some extent - at least when relating to living beings - with observable sex: “la mujer” is feminine and “el hombre” is masculine.
However, some languages have far more than three “genders,” most of which have nothing to do with biological sex traits. “Cylindrically-shaped things,” “flat things,” “some inanimate things that are neither cylindrical nor flat,” and so on.