Your objective should always be clear communication so keep things plain and simple. Acronyms are in this category too as they can create an 'Alphabet Soup' as not everyone knows what SINGARS stands for (Single-Channel Ground-Air Radio System), and really, why should they? A good rule to remember is that most big things have a small name (war, peace, day, night, sky, sea, etc.)
Jargon is technical language and is therefore only really useful for those in your industry. Avoidance is not about dumbing down but ensuring you are understood. While a doctor will use medical language with other doctors they adjust their choice of words when speaking to a patient or relative.
Some phrases are used in a variety of industries but they are still not the best decision. Those weekly 'brown bag lunches' could just as easily be called lunchtime meetings (with no lunch provided).
I had a manager who liked to play Buzzword Bingo in the boardroom. He was the CEO so felt no shame in shouting "House!" when he filled his card. There are lots of versions so do try it to get you through your weekly team meetings.
Another large organisation where I worked liked 'cascading' which is a bit like Chinese Whispers as the news gets mutated down the line of command so the people at the bottom only hear a fraction of what the bigwigs shared.
The Plain English Campaign is well worth reading and their Gobbledygook Generator will probably remind you of business papers you've read lately.
If you need to 'hit the ground running' and want colleagues to 'think outside of the box' or get 'on the same page' then the next time you use the 'open door policy' to 'touch base' on a 'level playing field' before some 'downtime' do be aware how ridiculous that all sounds.