3 sentences

1. 他的具体归期还不定。

   tā de jù​tǐ guī​qī hái bù​dìng.

   His exact return date is still undecided.

   Source: Dong Chinese Dictionary

2. 他最近心神不定，好像有什么心事。

   tā zuì​jìn xīn​shén bù​dìng, hǎo​xiàng yǒu shén​me xīn​shì.

   He has been restless lately, as if something is on his mind.

   Source: Dong Chinese Dictionary

3. 这种植物会长出不定根。

   zhè zhǒng zhí​wù huì zhǎng​chū bù​dìng gēn.

   This plant grows adventitious roots.

   Source: Dong Chinese Dictionary