Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
invŏlūtĭo, ōnis, f. [involvo], a rolling up, gathering of itself together: corporis spirae similis sive canina involutio, Cael. Aur. Acut. 3, 11, 103; concr., that which is inwrapped or infolded, Vitr. 10, 11.