to measure: to find or mark out the size, length, area, or amount of something against a standard.
At its core this is the plain, practical act of measuring: laying a measuring line along a wall, pacing off a boundary, or filling a standard container to see how much grain you have. Most of its appearances are exactly this. The book of Ezekiel uses it dozens of times for the visionary tour of a temple whose every gate, court, and wall is carefully measured out, and the law uses it for marking off land. So the first thing to know is that the word is concrete and everyday before it is anything else.
From that concrete base the word reaches in two natural directions. One is to measure something out to a person, that is, to portion it out: God measures out a defeated land, or measures back to people the wages of what they have done. The other is the flip side, what cannot be measured at all. When a writer wants to say a thing is beyond counting, like the stars or the sand on the shore, he says it cannot be measured. That is still the same act of measuring, just stated as an impossibility to stress how vast something is.
One striking image stands a little apart. When the prophet Elijah revives a dead boy, he stretches himself out over the child, body to body, three times. The verb there is this same word for measuring, used for laying one's own length against another. English Bibles render it stretched himself, and that is the sense, though it grows out of the idea of measuring one length against another.