When you choke, you are suddenly unable to breathe, often because something is stuck in your throat. Your dad's rude joke might make you gasp and choke on your grilled cheese sandwich.
You might choke in a smoky room, or choke on a grape that's lodged halfway down your throat. In either case, your body can't get enough oxygen. People also choke up with emotion, figuratively choking on their sobs. Likewise, a child might complain, "This scarf chokes me!" — it's uncomfortably tight, but he's not literally unable to breathe. When the weeds in your garden outnumber the vegetables, you can also say they choke, or crowd, your plants.