Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ob-tŭĕor, ēri (archaic inf. obtuērĭer, Plaut. Am. 3, 2, 19.
A collat. form, obtŭ-or, is assumed to explain indic. pres. obtuĕre, Plaut. Most. 1, 1, 66; 3, 2, 153; and inf. obtŭi, Att. ap. Non. 160, 1; Trag. Rel. v. 285 Rib. al.), v. dep. a.