Wow, that’s the best you can do, Super Dictionary?
“Thing?” Just a “thing?”
Nevermind that buttons often have holes all the way through, and that the only type of button that doesn’t have holes all the way through are shank buttons (I’m kind of craftsy and I know these things — so sue me).
Maybe you could go so far as to venture “a small, round, flat disc with holes.” Or some other descriptor than “thing.”
Then again, this is the last page of the letter B. Something tells me the writers were getting a little antsy to move on to C.
But let’s just blame this shameful definition of “button” on King Creepy McCreeperson.