Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ātrĭplex, plĭcis (more ancient form ātrĭplexum, i, n., Paul. ex Fest. p. 29 Müll.), n. (m., Plin. Val. 4, 7; f., Aemil. Macer Cap. de Atripl.), = ἀτράφαξις, the orach, a kitchen vegetable, Col. 10, 377; 11, 3, 42; Plin. 19, 6, 31, § 99; 19, 7, 35, § 117; 20, 20, 83, § 219; Pall. 5, 3, 3.