the oxide of a particular element (that has multiple oxides) having the smallest proportion of oxygen
that one of a series of oxides having the lowest proportion of oxygen. See Proto-, 2 (b)
Origin: [Proto- + oxide: cf. F. protoxide.]
Chambers 20th Century Dictionary
prō-tok′sīd, n. the first oxide—that is, an oxide containing one equivalent of oxygen combined with one equivalent of a base.
The numerical value of protoxide in Chaldean Numerology is: 7
The numerical value of protoxide in Pythagorean Numerology is: 9