I have accepted the word "selfish" to best describe my moral code since reading Rand's "The Virtue of Selfishness". It has not been easy to convince folks that "selfishness" is a good thing..., but I remain steadfast in my conviction!
Greed is essentially the desire for more (despite the popular addendum of "than an individual needs or deserves"). The desire for more what? This can be answered by more money, another car, more friends, etc; in essence; values. This in turn is the motivating force (desire) for bringing about activity in an individuals life to acquire more along the lines of those values . . . the virtues of production, creativity, etc, as the means of achieving those ends.
The popular notion that greed is the 'excessive' desire for more than an individual needs or deserves, is projecting a personal judgment as the guide for someone other than themselves. Who determines what is excessive? Who am I to say how much is enough for you or vice versa? Who am I to say what specifically how much or what you should value in general (outside of prohibiting what can be demonstrated to be immoral, that is.) Even if we apply 'excessive" to 'desire', as the desire can serve as the motivation, it still stands, as: who is responsible for deciding how much motivation another should/ought have?
If you want to defend selfishness, you will be hard-pressed to do so if you concede defeat the instant your adversary appeals to the "G" word (greed). What makes selfishness ok but greed not? Isn't it rationality that most fundamentally matters? Is greed in any form necessarily and inescapably irrational? If there can be rational selfishness, why can't there also be rational greed?
Altruists, of course, will insist that "rational greed" is an impossible contradiction in terms. They may also try to insist that the same goes for "rational selfishness." But it is specifically rationality and what it means that must be defended, regardless of altruistic assumptions about what selfishness and greed both allegedly include and imply.
An Objectivist view of selfishness and/or greed moderated and driven by rationality will very likely be judged by altruists to be a strange if not bizarre view of selfishness and greed, not representative of "true" selfishness or greed at all. Altruists want selfish/greedy people to be obsessed with conquering and exploiting others for personal gain at all costs, rather than steadfastly dedicated to rationality (on principle) in all production and trade (including non-material trading as well as purely material forms of trade -- which is another integation altruists typically seek to disintegrate, preferring to assume that "trade" means economic or material trade only). People who fit the typical altruist view of selfish greed give altruists the perfect fodder for altruists' outrage and condemnation, with the issue of rationality versus irrationality completely lost in the confusion (perhaps intentionally so, to keep altruism safe from the light of reason).
Several formulations in comments by the questioner may be confusing or even misleading to a general audience.
1) "I have to turn in my Objectivist card to establish..."
If this means explaining that Objectivism is a new and revolutionary philosophy that challenges altruism, then yes, it is and does.
2) "selfish pursuit of [unlimited] wealth is [by definition] NOT 'greedy'"
When altruists use the term "greed," they tend to be focused on the beneficiary of values rather than issues such as the standard by which "value" is to be judged at all, and how values come into existence. They probably see greed as an extreme unwillingness to "share" values with others, and probably regard the idea of "trade" as inherently exploitative of others, especially successful trade in which one receives a greater value to oneself in return for giving up a lesser one. This isn't an issue of how one defines "greed," but an issue of how one pursues it, i.e., how one pursues one's own interests.
3) "irrational, self destructive pursuit of wealth IS [by definition] 'greedy'"
Again, it's not an issue of how one defines "greed," but how one pursues it. At root, altruists aren't focused on what is self-destructive or self-beneficial; they are concerned mainly with how one treats others and responds to them. That's what "altruism" means -- "other-ism." They can't see (and don't want to see) how trade (both material and non-material) can be mutually beneficial for both sides in the trade, or how capitalism is a vast system of cooperation rather than "dog-eat-dog" competition.