Talk through your hat (hablar sin saber)

Idiom Communication

Meaning

To speak nonsense or about something one knows little about.

Hablar tonterías o sobre algo que uno sabe poco. (hablar tonterías o sobre algo que uno sabe poco)

"He was talking through his hat about quantum physics."

"Él estaba hablando sin saber sobre la física cuántica." (él estaba hablando sin saber sobre la física cuántica)

Knowing a small amount about something can lead to mistakes.

a limited or quiet release of a new product before the full...

an attempt to obtain sensitive information by deceit

to take on someone's role or responsibility

to travel with very little luggage

to increase effort or commitment toward something