I am wondering the exact same thing. Recently I've simply been ignoring the definition google offers at the top but after once again seeing an incomplete/incorrect definition I decided I had to try and see any source at all and nope, nada, not even sure if it's google's doing or what, but the word I looked up was 'FETUS', a fairly significant word in our lives, and it was defined as "an unborn offspring of a mammal, in particular an unborn human baby more than eight weeks after conception." The 2nd part is okay (doesn't mention when the fetus stage ends), but the first half states fetuses only apply to mammals. What about birds? And other vertebrates?? I majored in biology but thought this as more a common knowledge thing -even dinosaur embryos had a fetus stage. I checked Encyclopedia Britannica and they had it right:
"Fetus, also spelled foetus, the unborn young of any vertebrate animal, particularly of a mammal, after it has attained the basic form and structure typical of its kind."
If we are to live by google, then we will grow dumber by google if it is the main source of defining what a word is, especially when they do it in such a watered-down inaccurate way. I mean what are words to human society other than being essential for communication and vital for creating laws and commerce across the globe. They can literally change the definitions of words in any search engine language they support, whether on purpose or by accident it's not a good thing to have put into the hands of one massively powerful global entity, and quite frustrating too lol.