means A hypothetical tunnel through spacetime that links two distant points, in theory letting you travel between them without crossing the space in between.

from A plain compound of "worm" and "hole" — the literal image is the tunnel a worm bores through an apple, where the surface route around the skin is long but the chewed shortcut goes straight through. Physicists John Wheeler popularized the term in the 1950s for the spacetime structures that arise in Einstein's equations; earlier, in the 1930s, Einstein and Nathan Rosen described the same geometry, still called an "Einstein–Rosen bridge." The homely apple-worm metaphor stuck because it captures the idea perfectly: the universe as the apple, the wormhole as the burrow that beats the long way round.