Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ĭn-argūtus, a, um, adj., not acute, without acuteness (post-class.): sententia non inarguta, Dig. 7, 5, 5, § 1.
Adv.: in-argūtē, not acutely: non mehercule inargute nec incallide opposuisti hoc Tullianum, Gell. 12, 13, 19.