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motionlessly (e.g. stand, wait); (be) still
fixedly (e.g. gaze, stare); intently (e.g. listen, think)
patiently (endure); stoically
firmly (e.g. hold); restrained
じっとしていられない性格なんです。
I have a personality that can't stay still.
彼女はじっと黙って話を聞いていた。
She listened to the story in silence without moving.
痛みをじっと堪えて治療を受けた。
I endured the pain silently and received treatment.