An incubator occupant is a person or creature that is housed in an incubator, which is a device used to maintain a stable environment for the occupant. The four crossword solutions for this term are EGG (3 letters), infant (6 letters), NEONATE (7 letters), and NEWBORN (7 letters). An EGG is the first stage of development for many species, including humans. An infant is a young human child from birth to 12 months old. A NEONATE is a NEWBORN baby up to 28 days old. A NEWBORN is a baby from birth to 4 weeks old.