Yes, many of us are too likely to interpret the word "estimate" at face value. It is a wonderful idea to view this instead as only a starting point -- an information-gathering conversation -- as how to provide your customer or other stake-holders what they need.
If you are some combination of lucky, influential, and persuasive, you might have some ability to shape the contours of their expectations. :)
It's easy to detect this:
Gently begin a discussion of how much uncertainty is tolerable, do they want to know the number we are 50% likely to hit? 80%?
If you get emotional pushback to discussing uncertainty, they are looking for a promise.