Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
transŭo or trans-sŭo, sŭi, sūtum, 3, v. a., to sew or stitch through; to pierce through (not ante-Aug.): exteriorem partem palpebrae acu, Cels. 7, 7, 8: mediam partem subulā, Col. 6, 5, 4: exta verubus, Ov. F. 2, 363: ad ipsas radices per medium acu duo lina ducente, Cels. 7, 7, 11.