stink
To smell very bad or have a very bad smell.
To stink means to smell really bad. When milk sits out too long and goes sour, it stinks. When someone forgets to take out the garbage for a week, the kitchen starts to stink. The smell of a skunk is so powerful that we call it a stink, and rotten eggs are famous for their terrible stink.
The word also means to be very bad at something or to be of poor quality. If you say a movie stinks, you mean it was awful and not worth watching. When someone says “I stink at drawing,” they mean they're not good at it (though with practice, that can change). A bad situation might also stink: “It really stinks that the field trip got canceled because of rain.”
You might hear the phrase raise a stink or make a stink, which means to complain loudly about something unfair. If students made a stink about not having enough time for lunch, they're protesting strongly and making sure adults pay attention to the problem.
The animal connection is strong here: a stink bug releases a foul odor when threatened, and anything described as stinky smells unpleasant enough that you want to move away from it quickly.