What does "preemie" mean?

Premature baby. It's a medical slang and it corresponds to a baby, who was born less that 37 weeks of gestational age.
A baby born early. Any baby born before 37 weeks is considered a "preemie" or premature baby. There is a huge range in how well preemies do, however, depending on how early they are.

Related Questions

Intl adoption, what does this mean regarding preemie eye exam: fundus: both plus (-), full vascularization, no rop rec; fix & following eom, cr (@2yo)?

It means. The retinas have no rop (retinopathy of prematurity) and the baby should have a cycloplegic retinoscopy (a measurement) at age 2 years old. However I would recommend that you arrange for the baby to be seen by a pediatric ophthalmologist soon. Premature babies are prone to many eye problems and should be followed by an expert.
Infant eye exam. Both eyes hyperopic but may be myopic in future, normal vascularization, no rlf signs, fixates on objects and can follow their movement, repeat exam in 2 yrs..