Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ŏpĕrātĭo, ōnis, f. [operor], a working, work, labor, operation (not in Cic. or Cæs.). 
- I.  In gen.: insidiantur aquantibus (apibus)  ranae, quae maxima earum est operatio, cum sobolem faciunt, Plin. 11, 18, 19, § 61; 11, 24, 28, § 80; Vitr. 2, 9.
 
- II.  In partic. 
 
- A.  A religious performance, service, or solemnity, a bringing of offerings: operationes denicales, offerings, Fest. s. v. privatae feriae, p. 242 Müll.; Inscr. a. 286, p. Chr. ap. Orell. 2234.
 
- B.  In Christian authors, beneficence, charity, Lact. 6, 12; Prud. Psych. 573.