Synonyms for Infant:

adj.

beginning (adjective)
precursory, initial, new, aboriginal, fetal, inaugural, infantile, alpha, incipient, primal, budding, original, newborn, introductory, baby, embryonic, early, preparatory, formative, beginning, maiden, sprouting, primeval, first, Commencing, foremost, starting, hatching, germinal, genesis, nascent, primordial, Dawned, preliminary, emerging.
callow (adjective)
green, young.
earliest (adjective)
original.
green (adjective)
green, budding, sprouting.
infant/infantile (adjective)
immature, initial, baby, youthful, juvenile, early, nascent.
initial (adjective)
embryonic, germinal, Commencing, incipient, inaugural, introductory, original, first, foremost.
juvenile (adjective)
formative, infantile.
original (adjective)
primeval.

n.

accredited, business, bloated, tot, little one, all-night, business-to-business, anticompetitive, big, brick-and-mortar, brisk, collective. bairn, foundling, blue baby, neonate, designer baby, nursling, bundle of joy, youth, bambino, babe in arms, feeder, kin. law. green, youthful. babe (noun)
little one.
bambino (noun)
bundle of joy.
infant (noun)
child, young, kid, newborn, immature, babe, baby, bairn, neonate, bambino, infantile, toddler, little one, tot.
juvenile (noun)
boy, girl.
kid (noun)
lad, lass.
nursling (noun)
nursling.
tot (noun)
tot.
young person (noun)
kid.
youngster (noun)
kid, fledgling, sprout, girl, lad, stripling, juvenile, toddler, waif, sprig, slip, minor, sapling, youngster, boy, urchin, child, lass, innocent.

Other synonyms:

designer baby, bairn, bambino, bundle of joy, neonate, nursling, foundling, blue baby. babe in arms. youthful. feeder. child
tot.
Other relevant words:
immature, law, business-to-business, bundle of joy, babe in arms, feeder, babe, bairn, big, business, bambino, all-night, collective, green, foundling, youth, young, accredited, kin, tot, nursling, brick-and-mortar, little one, youthful, neonate, bloated, anticompetitive, brisk.