Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. in-frēnātus (infraen-), a, um, adj., without a bridle: equites frenati et infrenati, on unbridled horses, Liv. 21, 44, 1.
Trop.: lingua, Cassiod. Hist. Eccl. 12, 4.
2. infrēnātus, a, um, Part., from infreno.