Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
longĭuscŭlus, a, um, adj. dim. [longior, -ius], rather long (very rare): versus, Cic. Arch. 10, 25.
Hence, * adv.: longĭ-uscŭlē, rather far: progredi, Sid. Ep. 8, 11.