Brachyptery is an anatomical condition meaning that an animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

 has very reduced, non-functional wing

Wing

A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...

s. Such as animal may be described by the adjective

Adjective

In grammar, an adjective is a 'describing' word; the main syntactic role of which is to qualify a noun or noun phrase, giving more information about the object signified....

"brachypterous".

A brachypterous wings are very common in the insect world when the insect give up the ability to fly hence reduce it's fly muscles so save energy. This condition is known in parasitic insect that lives on other animals, insect in isolated oceanic islands without natural enemies or even females that use the extra benefit energy to manufacture more eggs.
Sometimes brachypterous insects can exist with fully developed wings (macropterous) individuals or wings development depends on the temperature so in cold winter wings are reduced and in summer they are full develop for immigration.