(excuse me for my not good english)
This happens me once in a while and happened lately: I am in a meeting in the same room with my client and someone (one person or more) from a web agency, or some company's salesman, or someone from marketing department.
This third person start to embellish the talk with totally unnecessary technical jargon, abstruse words, acronym, and similar, sometimes even without knowing exactly or deeply what is under these words.
I know exactly what is happening, that person wants to mesmerize/impress the other present people like: "I know everything, I am a guru and you are noone in the field so you must shut up and trust me 100%, now sign the contract". (Then the client will get some scam service or similar.)
The fact is that this person could have explained the same things using normal simple words and concepts, thing that most of the times I do after the main meeting, me and the client alone.
Imagine the client who can be a 68 years old very expert carpenter or a young chef but with very little or zero computer/internet/e-commerce/etc. knowledge and he wants me to be present for any help or consulence.
Now happened a few times that this third person says one or more abstruse word or acronym that the client expects me to know, but I don't know because it's not exactly my field even if it's close, or it's something that I knew but in the moment I don't remember, or simply I have never encountered since now.
What is the best answer or behaviour to have in this situation to avoid to give the impression of incompetence, appear confused, or avoid to give clumsy answers to the present people?