Page with no description for search engines
The search engine builds the result text from whatever it finds. Sometimes it gets it right. When it does not, that is the first sentence anyone reads about you.
When we count it as met
When we measure the same pages again, all of them declare a meta description.
How to check it yourself
Confirm it in the page head: the meta description tag appears with its text.
Measure it on your site
UXMachine measures it in a real browser, on desktop and mobile, together with the other checks.