The story
Goûter is the French verb 'to taste', from Latin gustare, the same root as déguster and the English gusto. Used as a noun, it means the snack in the late afternoon, and above all the one French children expect when they come home from school. It is also called the quatre-heures, after the time it is eaten.
It used to be bigger. Until the 18th century the goûter could be a full cold meal in the late afternoon, and it shrank as the habits around it changed. Today it is mainly for children: a slice of bread with a bar of chocolate, a few biscuits, a piece of fruit, a glass of milk. Adults are supposed to have grown out of it, and many quietly have not.
English has borrowed the word before. In the early 20th century it turned up in English writing as a dated term for a light afternoon meal. Since the French spelling reform of 1990 the circumflex is optional, so gouter without the hat is now correct French too.
The obvious English match is afternoon tea, but that suggests scones and a tablecloth. Teatime in parts of Britain can mean the evening meal itself. The goûter sits between the two: a fixed, small, unfussy pause that belongs to childhood.
Picture a school gate in Lyon at half past four. Parents hand over paper bags and children are eating before they have reached the corner.