a model or figure of a thing's shape: either a plan to build from or a likeness of something that already exists
The word comes from the ordinary verb "to build," so at root it means something built: a structure, or the design behind one. From that single idea it fans out in a few directions, but always naming a representation of some thing's shape, whether that thing is still to be made or already stands in view.
In its best-known use it is the God-given plan for a sacred building. Moses is shown the model of the tabernacle on the mountain, and David hands Solomon the plan for every part of the temple. Here the word points forward: a design the builder is to reproduce faithfully.
But the word points the other way just as often, at the figure or form of something that already exists. It names the shape of a creature that an idol-maker copies, the image people bow to, and the form of a hand or a living thing that a prophet sees in a vision. Sometimes it is simply a copy of a structure, like the replica altar the eastern tribes built by the Jordan.
Because one word covers both a plan to build from and a likeness of what is already there, English has to reach for several words for it. It sits close to דְּמוּת, "likeness," and to the Greek τύπος that later writers used when they quoted the command to build "after the pattern."