Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
stĭmŭlātor, ōris, m. [stimulo], a pricker-on, instigator, stimulator, Claud. ap. Ruf. 2, 501; Mamert. Grat. Act. ad Iul. 5 (in Cic. Dom. 5, 11, Orell. and B. and K. read instimulator); Vulg. Jer. 46, 20.