1. An exclamation expressing pain, discomfort, or the sound of a physical impact.
Usage: informal; often used to react to being hit or to sympathize with someone's pain
2. An exclamation expressing sympathy, concern, or acknowledgment of an awkward or unfortunate situation.
Usage: informal; used to react to bad news or embarrassing moments

Examples

• Oof! That ball hit me right in the stomach.
• He fell off the ladder and yelled 'Oof!' as he landed.
• Oof, that's an awkward situation you're in.
• Oof, I can't believe they said that in front of everyone.
• When she tripped on the stairs, everyone heard her oof from the bottom.
• Oof, that test was harder than I expected.