Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
rūmen, ĭnis, n. (collat. form rūma, ae,f., Arn. 7, 230 dub.; Serv. Verg. E. 6, 54), the throat, gullet: rumen est pars colli, quā esca devoratur, unde rumare dicebatur, quod nunc ruminare, Fest. p. 270 Müll.; cf. Paul. ex Fest. s. v. adrumavit, p. 9 ib.: ruminatio dicta est a rumine eminente gutturis parte, per quam demissus cibus a certis revocatur animalibus, Serv. Verg. E. 6, 54; cf. Isid. Orig. 11, 1, 59; 12, 1, 37: dum sit, rumen qui impleam, Pompon. ap. Non. 18, 16 (Com. Rel. v. 153 Rib.); Fest. p. 270, 28 Müll.; Paul. ex Fest. p. 9, 14 ib.