不三不四 [- sān bú sì]①(不像样子) neither fish， flesh nor fowl; neither one thing nor the other; (These men) are not this and not that.②(不正派) suspicious (characters); dubious; shady; with no character; nondescript:
•¶ 不要和一些不三不四的人来往。 Don't get on with dubious characters.