I think pspell is the wrong approach: misspellings can and do happen -- and of course there are words like proper nouns that even if spelled correctly might trigger an error in pspell.
We had a similar issue with account signups on our website. More or less random information was being used to create the account. It turned out (not surprisingly) that all of these fake submissions were created by bots, so we added a captcha to our sign up form and the problem was solved. It wasn't a huge problem to begin with, but we went from a couple of dozen fake accounts a day to basically zero.
For our purposes, we decided to use reCAPTCHA v3 because it doesn't even require any user interaction, it was easy to set up, and it was free (see: https://developers.google.com/recaptcha/docs/versions). That said, there are dozens of alternatives should you prefer. Regardless, judging by the type of data you're getting, I'm pretty certain your issue is being caused by bots too and a captcha or other human-verification system should solve your problem.
As an aside, you may wish to check your log files to see which networks, countries, etc. are responsible for these fake submissions. My guess is you'll start noticing some patterns. We did. So we tightened up the security checks for certain types of data coming from certain countries -- and banned other networks entirely from accessing our system (think: large, shady server farms in countries where internet lawlessness is rampant.) If you decide to go the ban route, you can do so on the application level (such as in your PHP scripts), in your web server configuration (e.g., httpd.conf) or by using a third-party service such as CloudFlare. (In addition to doing IP checks, CloudFlare allows you to ban entire ASNs which I find super useful.)