American & Australian, British & Australian, Australian

to say that something is completely true, especially when someone does not believe you.

He swore up and down that he'd never seen the letter.

If I ask her, I know she'll swear blind she locked the door.

He swore black and blue he had nothing to do with the missing money.

• under the circumstances
• under the counter
• under the gun
• under the influence
• under the knife
• under the skin
• under the sun
• under the table
• under-the-table
• under the weather
• under the wing of
• under the wing of something
• under the wire
• under thumb
• under wing
• under wraps
• under your belt
• under your breath
• under your nose
• under your own steam
• under your wing
• until are blue in the face
• until hell freezes over
• until kingdom come
• until the cows come home