Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sŭper-lābor, bi, v. n. dep., to glide or run over (very rare): in aperto jacentes sidera superlabebantur, Sen. Ep. 90, 42; Sid. Ep. 1, 2 med.; Liv. 30, 25, 6 (dub.).