Interjection

1. An expression of one's own physical pain.

   Ouch! You stepped on my toe! That hurt!

2. An expression in sympathy at another's pain.

   Ouch! Her sunburn looks awful.

3. A reply to an insult (frequently one that is tongue-in-cheek or joking).

   Ouch. How could you say that?

4. An expression of disappointment.

   Ouch, I really wanted to do that.