What is the meaning of Crucible?

A cup-shaped piece of laboratory equipment used to contain chemical compounds when heating them to very high temperatures.

A heat-resistant container in which metals are melted, usually at temperatures above 500°C, commonly made of graphite with clay as a binder.

The bottom and hottest part of a blast furnace; the hearth.

A very difficult and trying experience, that acts as a refining or hardening process.

Source: wiktionary.org