Real Dictionary

anvil
You can refer to a difficult experience that changes someone or leads to something good as a particular type of anvil.
countable noun: An anvil is a heavy iron block on which hot metals are beaten into shape.
countable noun: The anvil is the middle bone of the three small bones in the ear of mammals.

anvil in American English
an iron or steel block on which metal objects are hammered into shape
noun: a heavy iron block with a smooth face, frequently of steel, on which metals, usually heated until soft, are hammered into desired shapes

anvil in British English
noun: a heavy iron or steel block on which metals are hammered during forging

anvil in Mechanical Engineering
noun: An anvil is a fixed part of a measuring device. The piece to be measured is held against it.