Shaf‘ prayer (a type of night prayer) (الشَّفْعُ)
العقيدة أصول الفقه
المعنى الاصطلاحي :
The two "rak‘ahs" (units of prayer) preceding the Witr prayer.
التعريف اللغوي المختصر :
"Shaf‘": even number. It is any number that can be equally divided by two, like two and ten. Opposite: "witr" (single, odd). Original meaning: joining two things. Other meanings: increase, association.