Definition - The use of one part of speech as another.

Example -
If you steal (verb) things that are on sale, they really are a steal (noun).

Etymology -
The word derives from the Latin convertere, turn around or transform (from com-, together + vertere, to turn).

Oxford English Dictionary -
Its first citation is from 1928:
"It seems to me more logical to say that the adjective is converted and to call the result a conversion-noun than to use the term converted noun in the latter sense."
(Bergener Conversion of Adjs. into Nouns 2)

Please comment