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Your question isn't clear.
What do you mean by point?
What do you mean by defined?
if f(x) = 1/x, then the function is undefined at x = 0 because it's definition cannot be evaluated at that point on the real line. The point (x,f(x)) on the Cartesion plane also has no meaning for x = 0, so perhaps you can say that that point is undefined but I suspect this isn't what you're thinking...
The example you've given doesn't suggest that the point at (2,1) is undefined--on the contrary, it is very well defined 'cause you defined it to be (2,1)!
Not only that but the function you've describe (as little as you described it) isn't even particularly interesting. Perhaps it was not your intention but your function is still continuous. What you said was:
lim(x->2)f(x) = 1 and f(2) = 1
Perhaps you meant to say something like this:
lim(x->2)f(x) = 3 and f(2) = 1
...? Even in this case, while the function is discontinuous, it is still well defined at x = 2.
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