Certain or definite; used to indicate that something is clear or sure (often appears as 'not certain' — 定かではない).
目撃者の証言は定かではなく、結論を出せない。
The witness's testimony is not certain, so a conclusion cannot be drawn.
事件の原因はまだ定かになっていない。
The cause of the incident is not yet clear.
彼女の行き先は定かだが、時間は未定だ。
Her destination is certain, but the time is undecided.