In The Little Prince," It's a quote that sometimes pops into my head when people are asking for my advice through design mediation, especially when both sides are saying "I have no clue what they want!"
As with most things, both parties are generally partly to blame for the a breakdown of communication and trust, and two pieces of advice could go a long way to solving the problem(s).
1) It's okay to say you don't understand something
This is true for both the designer and the client. If there is something that's confusing, it's better to say so than to pretend you understand what's happening. If either side is using vague or technical language, don't be afraid to ask for clarification.
Don't agree to something that you don't completely understand.
2) Don't mock somebody for not knowing
If you went to the doctor and they said you had cephalalgia, then mocked you for not knowing what it is, you'd probably think they're a bit of a dick and not go back. If you went to another doctor and they said you had a headache, told you not to worry, and gave you easy to follow advice to treat it, you'd probably be a lot happier.
The same applies to whatever field you're working in. If you're a designer, don't assume that everybody knows what a wireframe is, what kerning is, or exactly what shade #002fa7 is. If your field is law, don't assume that Latin phrases like caveat emptor and de minimis non curat lex are widely understood just because you happen to use them a lot.
It's never okay to mock somebody about something they don't know, especially when they have no background in the field you're discussing. You don't know how much they know about other things, so don't demean them for not knowing about your specific area of interest and/or expertise.
If in doubt, ask the other person for clarification, and make sure you both completely understand what's going on.