(Norse mythology) a huge ash tree whose roots and branches hold the earth and heaven and hell together

Usage examples of yggdrasil.

I regard the huge old tree and listen for its echoes down the ages: Yggdrasil, the Golden Bough, the Yule tree, the Tree of the Knowledge of Good and Evil, the Bo beneath which Lord Gautama found his soul and lost it.

The aged ash tree Yggdrasil was shaken from its roots to its topmost branches.

In the nearby volume of space, collimated beams of accelerated matter were traveling in the same relativistic frame as Yggdrasil and shedding some of their radiation in the visible part of the spectrum.

There was nothing to see out there anymore except Yggdrasil itself—mile after mile of great twisting subbranches and carpets of leaves, lit up by the banks of spotlights that were trained on them from the shaft of the probe: not only to give Yggdrasil a sense of its own rotation, but to provide the human passengers with a sense of place in a universe that otherwise had gone blank.