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

   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 at will

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)

   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!