To stand to attention is to stand stiffly straight, as a soldier does. Told to stand to attention.
The heels go together and the hands go flat at the sides, and nothing moves. To stand to attention for long enough makes people faint, which is why they are told to flex their knees.
1phrasestand to attentionTo stand stiffly straight, as a soldier does.
“They had to stand to attention for forty minutes in the sun.”
stand to attention is a posture.
Practised in Body Language & Gestures