A sneeze is a sudden burst of air that comes out of your nose and mouth. It's usually caused by something getting into your nostrils or sinuses.
When someone lets out a big "Achoo!" it means they're having a sneezing fit, but more often we use the word to describe one single sneeze. You might say "I just had the worst sneeze ever" and people will know exactly what you mean. It's also common for us to joke around about someone who always seems to sneeze at exactly the wrong moment - like when they're giving a presentation or in a quiet library.
(intransitive, medicine) To expel air as a reflex induced by an irritation in the nose.
Example: To avoid passing on your illness, you should sneeze into your sleeve.
