油断も隙もない

ゆだんもすきもない

one must constantly be on one's guard with ...; one cannot be too careful of ...

Also written 油断も隙も無い

Meanings

Expression
one must constantly be on one's guard with ...; one cannot be too careful of ...

Example sentences

油断ゆだんも隙すきもない奴やつだ。

You can't let your guard down for a second around that guy.