说不定
Written shuō bu dìng, said shuō bú dìng — 不 becomes bú before a fourth tone.
Meaning
- can't say for sure
- maybe
Example sentence
你说不定知道他的名字？
Do you happen to know his name?
Characters in 说不定
说 to say plus 不定, not fixed. Cannot be said for certain, hence maybe — and 说得定 is not used.