Uh-oh (interjection)

1. An exclamation of surprise, dismay, or realization.
2. An expression of recognition that something bad has happened or is about to happen.

Origin:

20th century: imitative of the sound of hesitation or uncertainty.

Examples:

1. Uh-oh, I think we're lost.
2. He looked at the empty gas tank and said "Uh-oh".
3. She realized she left her keys in the car and said "Uh-oh".
4. He heard the sound of breaking glass and said "Uh-oh".
5. As the sky turned dark and the wind began to pick up, she said "Uh-oh" and knew it was going to be a bad storm.