語源不明（American Heritage Dictionaryによる）ということですが、専ら他動詞として、受身形で用いられるか、もしくは能動形で目的語を伴うことが多いです。
The Beatles have so far been the most prominent holdout from iTunes and other online music services, and Apple's overtures to put the music online have been stymied by the ongoing litigation.
(Apple, Beatles Settle Trademark Lawsuit. Associated Press. 2007.)
He criticized the President's proposal to tie increases in health-plan premiums to the general inflation rate. He said tight price controls would stymie efforts to increase quality and cost-effectiveness.
(Changing the Fortunes of the Medical Business. New York Times. 1993.)