know better (than to (do something))

1. to be wise enough to behave in a more responsible or acceptable way.

It was a stupid thing to do, and I thought she knew better.

You know better than to interrupt when someone else is talking.

Usage notes: sometimes used in the form not know any better:

Doesn't she know any better than to wear jeans to a place like this?

2. to be wise enough to know that you should not believe someone or something.

The guy who was trying to sell us the car said it was in great condition, but I knew better.

• be scared shitless
• be scared to death
• be scattered to the four winds
• be second to none
• be set in concrete
• be set in stone
• be several cards short of a full deck
• be shaking in boots
• be shaking in shoes
• be shaking in your boots
• be shaking in your shoes
• be shit scared
• be shitting bricks
• be short of a bob or two
• be shot of
• be shot of someone
• be shot of something
• be shot to hell
• be shot to pieces
• be sick and tired of
• be sick and tired of doing something
• be sick and tired of something
• beside
• beside the point
• beside yourself