Can "certain" be used as a synonym of "definite" in front of "answer"?
When I hear "a certain answer", I think about "a specific answer" not a "definite" nor "ultimate" answer.
Can a "certain answer" mean a "definite answer"?
"Certain" does have two different albeit related meanings.
Last week I met a certain Mr Jones.
This means that you mean a specific person.
I am certain that his name was Jones.
This means that you have good reason to believe you are correct.
In your example, it could mean either!
A certain answer.
It could refer to a specific answer, or that someone is sure of the answer they gave.
As always context is required to determine which it is.
If it were:
I am looking for a certain answer.
This sounds to me like someone is looking for a specific answer. Interestingly you may also hear someone refer to "a certain question", which can only carry this meaning that it is a specific question. Normally when the word is used this way it carries the meaning of something unspoken or unmentionable that everybody involved ought to know.
Can you give me a certain answer?
This sounds like someone is asking for a definite answer; that is an answer they are sure of.
The term "a Certain answer" is normally associated with a specific answer. I don't believe that there is a context in which "certain" could be synonymous with "definite" or "ultimate".
In this case, "a certain answer" carries the meaning that the speaker has in mind, and is waiting to hear, a very specific answer. So when they say "when I hear a certain answer", it is as if they are saying "when I they hear the answer that I have in mind".
"Definite" implies precision or a lack of uncertainty; "ultimate" implies a state of being ideal or excellence. However, in both cases, these refer to the general nature of an answer. They don't convey any context regarding the particular answer that the speaker has in mind.
One might expect that "a certain answer" implies that the speaker has in mind the "correct" answer, though that need not be the case.
Certainly! (pun intended)
Admittedly, it is off-putting, since you don't expect that meaning. When you see this type of thing, it usually results in problems of communication since the intended meaning is easily lost, however it can also be done on purpose to be witty.
A few examples that come to mind include: