Nitpick: I see that sort of phraseology frequently from Orthodox on this forum. If the term "valid" isn't Orthodox, what term is? Please, let's at least learn to speak each others' language, here. You apparently make a distinction between "a Baptism" and "a ceremony that sort of resembles a Baptism, but isn't one" ... what is the Orthodox term for the latter?
"Nitpick: I see that sort of phraseology frequently from Orthodox on this forum. If the term "valid" isn't Orthodox, what term is?"
AB, my post 79 started with a quote from CC's post 76. His words not mine. That said, "valid" probably isn't a term an Orthodox person would use. The issue is whether or not a person has received, in one of the many "ecclesial assemblies", to use the Pope's terminology, one of the Holy Mysteries (Sacraments) of The Church. Assuming for the moment that such Mysteries can be imparted by any ecclesial assembly, and I think The Church believes that in some instances they can be, then the Mystery of the ecclesial assembly is effective to transmit God's uncreated grace. The reason that the word "valid" probably wouldn't be used is because some may feel it bespeaks a certain legalism which is foreign to Orthodoxy. In the end, and on this particular issue, I doubt the terminology means much as far as it goes, though it may imply fundamental differences about how we perceive what the sacrament in question "does" to us.
"Nitpick: I see that sort of phraseology frequently from Orthodox on this forum. If the term "valid" isn't Orthodox, what term is? Please, let's at least learn to speak each others' language, here."
Orthodox resistance to using the term "valid" is primarily based on the RC practice of declaring certain sacraments by people outside the RCC to be "valid but irregular." This is most famously true of the concept of "valid orders" of vagante bishops whose "line of succession" is outside the Church...
The story was told of an Orthodox bishop who was approached by a Episcopalian priest at an ecumenical gathering early in the 20th c. The Episcopal priest asked the Orthodox bishop if he thought his orders were "valid."
The Orthodox bishop paused and asked the priest, "does your church consider your orders to be valid?" "Why, yes," the priest replied. The bishop's answer was simple: "then why would you need to ask me whether your orders are valid -- in what other church and under what other bishop would you want to exercise your orders other than your own?"
The only place where the nature of ceremonies done outside the Orthodox Church is any of our business is when someone is converting to Orthodoxy. Any other situation would involve great presumption in declaring *one way or the other* on what happens in non-Orthodox religious ceremonies.
As Coollidge nicely summarized, with additional good input from Kolokotronis and Kosta, there is a spectrum of opinion within Orthodoxy on the issues of how someone is received into the Orthodox Church. Most of the Orthodox Church tends towards caution in the first place, and I have observed a quiet trend, even in the more flexible American jurisdictions, toward a more strict practice of reception by baptism, blessing marriages by going through the Orthodox wedding ceremony, etc...
Now you ask: "You apparently make a distinction between "a Baptism" and "a ceremony that sort of resembles a Baptism, but isn't one" ... what is the Orthodox term for the latter?"
We call the one an Orthodox baptism. We don't presume to say anything about the other one. When one is received into Orthodoxy, the point is not what the person's former church didn't give him, but on the grace that the Orthodox Mysteries *do* give him.