Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mŏlīna, v. molinus.
mŏlīnus, a, um, adj. [mola], of or belonging to a mill, mill- (eccl. Lat.): saxum, Tert. adv. Marc. 4, 35.
Hence, as subst.