One response is to complain about it. The speaker is "clearly" using elitist language, using such words only to set his or her self above those that do not understand. The problem with this response is that not all people who use such words are doing so with the intention of having others being unable to understand. In fact, this would defeat the primary purpose of communication, which is conveying ideas to each other. Asking the speaker to use more common words seems like a reasonable request. We should realize, however, that the words that we do not understand are often a part of the speaker's world that they are common from the speaker's perspective.
A second response is to pretend to know what the speaker is talking about. Sometimes we can figure out the meaning based on context and, while we won't know the exact meaning of the word, will be able to figure out the general message. Unfortunately, we cannot always determine the meaning of the word, and the speaker's message, however good or important, is lost to us.
The third typical response is to take these situations as opportunities to expand our vocabulary. We ask the speaker (or others around us who may also know) to define or explain a word that is new to us. I cannot remember I heard this, but there is a quote that goes
A wise man was once asked, "How do you know so much about so much?" The wise man responded, "By never being afraid to ask questions about anything to which I am ignorant."Sometimes, the only way to know something is to ask the question. I think that, as a society, we have somehow decided that asking certain questions makes us less intelligent. The truth is quite the opposite. Asking those questions is how we gain knowledge. Admittedly, there are times when asking the question would not be appropriate. If there are any church words or theological terms that you come across and don't understand (like aumbry, thurible, ontological or epistemology), ask about them. Please remember that there are appropriate and inappropriate times to ask, though. I would appreciate it if you did not shout out, "What does epistemology mean?" in the middle of one of my sermons.