Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
cŏ-horresco, horrui, 3, v. inch. n., to shudder, shake, or shiver with fear or cold: nisi cohorrescit corpus meum, Aug. ap. Suet. Tib. 21.
In perf.: quem ubi agnovi, equidem cohorrui, Cic. Rep. 6, 10, 10; id. Att. 5, 21, 12; 7, 1, 1: ex quo (sudore) cum cohorruisset, id. de Or. 3, 2, 6.