to become many or much: to grow in number, amount, or extent
This is the verb at rest, reporting that something has become more: a family, a herd, a harvest, a run of years. It is the second half of the Bible's oldest blessing, "be fruitful and multiply," where the first verb (פָּרָה) names the bearing of offspring and this one names the swelling numbers that follow. Genesis says it over fish and birds, then over people, then again over Noah's household, and Exodus opens by reporting it as accomplished fact: the Israelites in Egypt grew so numerous that Pharaoh took fright.
The word is not confined to counting heads. What grows can be an amount of grain or silver, the reach of a road that has become too long, the greatness of God measured against a man, or the days of a life. Hebrew is content to use one verb for all of it, and the words around it tell you what is swelling. That range is why English translations reach for so many different words here: multiply, increase, be many, be great, be long.
The growth itself is morally neutral. Blessing increases, and so do enemies, sins, and sorrows. When a prophet or a psalmist uses this verb of wickedness piling up, that is no twist on its meaning: the warmth readers often hear in it comes from the company the word usually keeps, not from the word.