Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
circum-calco (in MSS. also cir-cumculco), āre, v. a., to tread or trample upon all around: codicem, Col. 5, 6, 21; id. 5, 6, 21, § 8: terminos, Sicul. Flac. p. 6.