to sow: to scatter seed onto the ground so that it can take root and grow.
At its root this is the farmer's word for the first step of growing a crop: flinging seed across an open field by hand so it falls into the soil and, in time, comes up. Everything the word does in the New Testament grows out of that picture, which would have been part of everyday life for the people who first heard it.
Because sowing is the plainest example of a small, hidden beginning that leads to a much larger result, the New Testament uses it again and again as a picture. Jesus turns it into the parable of the sower, where scattering seed stands for spreading God's message and the different ways people receive it. Paul stretches it further: the way you live now is a kind of sowing, and the harvest is what comes of it later, so that what a person plants is what they will reap.
Paul uses the same image one more time for death and resurrection. A body laid in the grave is like a seed put in the ground: what is buried looks like the end, but it is really a planting, and what comes up is more alive than what went down. In each case the literal act of sowing is the key that unlocks the picture, which is why all these uses stay recognizably one word.