勝手に

From 勝(かっ)手(て) (katte) + に (ni).

• (Tokyo) かってに [kàtté ní] (Heiban – [0])
• IPA^(key): [ka̠t̚te̞ ɲ̟i]

勝(かっ)手(て)に • (katte ni) 

1. selfishly; for one's convenience; wilfully, as one pleases
2. (especially in terms of inanimate objects) on one's own, by oneself; done in a way that does not require the assistance of another (person or thing)

   パソコンが勝(かっ)手(て)に再(さい)起(き)動(どう)する現(げん)象(しょう)

   pasokon ga katte ni saikidō suru genshō

   the phenomenon of one's computer rebooting on its own

   怖(こわ)かった、ドアが勝手(かって)に開(あ)いたんだ！

   Kowakatta, doa ga katte ni aita nda !

   I was so scared. The door opened on its own!

• 独(ひと)りでに (hitoride ni)

• 勝(かっ)手(て)にしろ (katte ni shiro): go to hell!, have it your way!