Definition of petit four in English:
 petit four
nounPlural petits fours ˌpɛtɪ ˈfɔːpəˌti ˈfɔːˌpɛdi ˈfɔr
A very small fancy cake, biscuit, or sweet, typically made with marzipan and served after a meal.
 Example sentencesExamples
-  And mignardises were exactly what I had in mind when I bought my new Flexipan molds, the one for little tartlets and the one for hemispherical petits fours.
 -  Inexplicably no one brought petits fours with our coffee, although they appeared together with coffee on the itemized bill.
 -  As a tea-time treat, we had some petits fours that I bought at the French cake shop the other day.
 -  It can also be baked lightly to make small biscuits and petits fours, akin to macaroons.
 -  The desserts are fabulous and with coffee and petits fours the bill came to £70 (inc G&Ts, a bottle of Chénas and a port).
 
Origin
  
French, literally 'little oven'.