Indeterminate; not fixed or decided; uncertainty or instability. Often used in written or technical contexts.
契約の条件はいまだ不定で、詳細はこれから詰める予定だ。
The contract terms are still undecided; details will be worked out later.
症状が不定で診断に時間がかかった。
The symptoms were vague, so the diagnosis took time.
不定の期間、入院が必要と言われた。
I was told hospitalization would be necessary for an indefinite period.