Listen - it goes a long way. What words are considered "suitable" are probably those used by the higher authorities. They probably don't understand technical jargon. If they don't use it, neither should you.
Confidence - this comes from a lot of practice along with a willingness to learn the right way. Don't be afraid to say, "I don't know, but will look into it." If you think this makes you look weak or incompetant, imagine what muttering and stuttering some worthless answer does for your career. Also, you have to come to the conclusion that you may be doing a fine job, but they are poor listeners. They're not as much of the authoity as you think.
Brevity - Edit your post for practice. Do we need to know you're a programmer? You could probably cut this in half.
Relax - It's not that bad. These people are no better than your friends or collegues.