Lewis & Short

nītĭbundus, a, um, adj. [nitor], pressing against, straining, striving (post-class.): mentium conspiratu tacito nitibundi, relying upon, Gell. 1, 11, 8: pondus nitibundum, oppressive weight, weighty pressure, Sol. 25, 12: caput, id. 27, 29.