Whilst the wrestling business as a whole has evolved a lot since the Attitude Era when WWE stars would be forced to live inside kayfabe, there are still many things that Superstars are not allowed to say.
When WWE is presented live on TV it is presented as a show, which means that it has to have a certain feel about it and certain words can ruin this illusion. Whilst some words and terms are added to the banned list on a regular basis, at present there is a long list of terms that Vince McMahon doesn't want his talents to use.
Belt/Strap
It appears that Vince McMahon doesn't like his Superstars to refer to their Championships as anything but 'Championship'. Calling them a 'belt' or a 'strap' demoralizes the importance of the Championship and WWE likes to keep their titles prestigious.
The Business/Our Industry
It's unknown why WWE doesn't like their Superstars to refer to the business or the industry in the way that many other companies do, but these terms are currently banned, which means that superstars have to think of new terms during promos.
Pro Wrestling/Pro Wrestler
It's obvious why these terms are banned since WWE is still trying to create the atmosphere of an entertainment show. Wrestlers are not actually seen as wrestlers, they are Superstars, but every now and then the term is used and WWE sweeps it under the rug.
Performance/Performer/Acrobatics/ Choreograph
Even though WWE is pushing forward the fact that wrestling is a show, they don't want their Superstars to be called performers. Instead, they must only be referred to as Superstars. Whilst the term Diva isn't actually banned, it may as well be since women can now only be referred to as Superstars as well.
House Show
This term was only banned a few years back when WWE decided to refer to their House Shows as "Live Events" instead to make them sound more important.
War
When The War Raiders were promoted to the main roster last year, they were called The Viking Experience before their name was changed to The Viking Raiders. This was done because WWE didn't want to use the term "War" on TV in this setting.
Sports Entertainment
Once again, this term was banned even though WWE is technically classed as Sports Entertainment because WWE wants to try to remain inside their Kayfabe bubble.
Hospital
This is another recent change, WWE decided that hospital didn't have the right sound to it, which means that commentators now use the term "local medical facility". When WWE wants something to sound much more serious, they allow commentators to use the term hospital.
Faction
WWE prefers to refer to their teams as "stables" or "group" which makes sense, but it's unknown why the term "faction" is frowned upon.
Feud/Fans
These two terms seem to break the kayfabe bubble and show that the people who are part of the show are aware that it's a show. Fans are known as The WWE Universe and Superstars are not allowed to call them fans.
Title on the line/the title changing hands
There was a confusing situation on RAW a few weeks ago when it was speculated that even the term non-title had been banned by WWE officials. This is just a way to make sure that the Championships remain prestigious.
Talent
As already stated, WWE Superstars are only referred to as such. "Talent" is a term used by outsiders rather than the stars who are on the show.
Shot
WWE used to refer to "title shots" but it appears that this was another term that was banned by officials.
Crazy
According to former NXT Star Taynara Conti, she used to shout "Are you crazy!" to her opponents whilst wrestling but was instructed by WWE discontinue it since they didn't want to use the term "crazy" wasn't one that they wanted to be used.
Interesting
Everything in WWE should be interesting, so it's likely that the company made the decision to take this term out so that commentators were not favoring certain segments over the others.
Coronavirus
WWE recently banned this term from being used as part of their show, which once again makes sense since the company doesn't want to focus on outside issues and would prefer to put on a show that allows fans an escape from the problems.