The Natural Philosopher wrote:
Norman Wells wrote:

No one said matter was converted into energy: We said MASS was.

"mass (Phys) The quantity of matter in a body" - Chambers Dictionary
of Science and Technology.

Care to tell us what abstruse definition you're using, and where it
may be found?

Not really. Chambers dictionary circa 1950 is probably geared towards
laymans usage, not what is used by scientists in pursuit of science.

That'd be why mine's dated 2000 then and is a specialist dictionary 'of
Science and Technology'.

Now, what obscure definition are you using, and where may it be found?