Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
nūtātĭo, ōnis, f. [nuto] (post-Aug.). 
- I.  A nodding: capitis, Plin. 11, 37, 49, § 135. 
- II.  A swaying. 
- A.  Lit.: frequens et in utramque partem nutatio, Quint. 11, 3, 129.
- B.  Trop., a shaking, tottering: nutatio reipublicae, Plin. Pan. 5, 6.