An orphan was a child without parents.
The orphaned Blakely children were taken to a police station on Carthedia which also acted as a poorly-kept orphanage when the Eleventh Doctor, acting as their guardian, was arrested for a hate crime by claiming the Daleks were evil. (PROSE: The Dalek Generation)
In 1965 Scotland, twelve orphans were removed from an orphanage called Holly Tree Lodge, ostensibly being taken to another orphanage, Harbour Heights. Instead, they were given to the 456 by Captain Jack Harkness in return for an influenza vaccine. The orphans were chosen because they "wouldn't be missed." (TV: Children of Earth: Day Four)
Some of the Doctor's companions were orphans, including Vicki Pallister (TV: The Rescue) and Victoria Waterfield. (TV: The Evil of the Daleks) Sarah Jane Smith had been orphaned as an infant. (TV: The Temptation of Sarah Jane Smith) Bernice Summerfield had been orphaned at age seven. (PROSE: Love and War)
In the 2410s, Darzil Carlisle was orphaned at the age of three when his parents were killed in a freak airlock accident, resulting in the Martian-born child being relocated to an orphanage in Finchley, north London. (AUDIO: The Game)