Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
infantārĭus, a, um, adj. [infans], that has to do with infants(poet. and post-class.).
Only substt.
I.infantārĭa, ae, f.,a woman fond of infants,Mart. 4, 88, 3.
II.infantārĭi, ōrum, m.plur.,sacrificers of infants, an epithet applied to the Christians, who were accused of offering up children, Tert. ad Nat. 1, 2.