Synonyms for Newborn (same or very similar meaning)
WordNet sense 1 (a baby from birth to four weeks):
neonate, newborn baby, newborn infant
WordNet sense 2 ((used of living things especially persons) in an early period of life or development or growth):
immature, young
WordNet sense 3 (having just or recently arisen or come into existence):
new-sprung
From the ODE community, based on WordNet
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