mandarin orange

Short definition from Wiktionary

Noun

1. 1
   A small citrus tree (Citrus reticulata) with oblate fruits smaller than the (so-named) sweet oranges.
2. 2
   The fruit of this tree; in loose, informal usage, the term may include other similar citrus fruits such as Citrus unshiu (satsuma or mikan).
3. 3
   Alternative letter-case form of mandarin orange.