bù sān bu sì

不三不四

neither three nor four

shady (person); sketchy; dubious; nondescript; neither one thing nor the other

Example:

不三不四的人
Bùsānbùsì de rén
person of dubious (or shady) character

交些个不三不四的朋友
jiāo xiē ge bùsānbùsì de péngyou
make friends with a lot of dubious characters

说些不三不四的话
shuō xiē bùsānbùsì de huà
make frivolous remarks; talk twaddle; irrelevant comments

自己生造的不三不四的词句
zìjǐ shēngzào de bùsānbùsì de cíjù
colourless expressions of one’s own making

和不三不四的人鬼混
hé bùsānbùsì de rén guǐhùn
hang around with shady characters

和不三不四的人来往
hé bùsānbùsì de rén láiwang
hang around with dubious characters

他听了这些不三不四的话非常气愤。
Tā tīng le zhèxiē bùsānbùsì dehuà fēicháng qìfèn.
On hearing these frivolous remarks he became furious.

他整天和一些不三不四的人厮混。
Tā zhěngtiān hé yīxiē bùsānbùsì de rén sīhùn.
He fools around all the time with some rather dubious fellows.

他老说些个不三不四的话, 讨厌！
Tā lǎo shuō xiēge bùsānbùsì dehuà, tǎoyàn!
He always says inappropriate things, really annoying!

他常和一伙不三不四的人瞎混。
Tā cháng hé yīhuǒ bùsānbùsì de rén xiāhùn.
He often hangs around with a bunch of dubious characters/He hangs out with a bad lot