A "rook" (ostensibly a contraction of "rookie") applies to soldier who has completed his or her basic training, but is still inexperienced. Usually this means a nugget who has completed his or her flight training and qualifications, but has little or no combat experience.
Kara Thrace teases Helo about flying with a rookie, referring to Boomer (Miniseries).
Chief Tyrol also refers to the deckhands tasked with damage control and fire supression after the first Cylon attack on Galactica as rooks (Miniseries).
Ensigns Brent Baxton and Joseph Clark are rooks that completed their training on the flight simulators available on Pegasus and are assigned to Galactica afterwards (Scar).