\Pro`to*met"als\, n. pl.
A finer form of metals, indicated by enhanced lines in their
spark spectra (which are also observed in the spectra of some
stars), obtained at the highest available laboratory
temperatures (--Lockyer); as protocalcium, protochromium,
protocopper, protonickel, protosilicon, protostrontium,
prototitanium, protovanadium. -- {Pro`to*me*tal"ic}, a.