Aloud

It was my own error. I didn't realize how long it had been since the youngest ate. Strapped into a forward-facing shopping cart at Babies R Us, he began to whimper and whine. The older woman just ahead of us decided she would let him know his antics were upsetting her day, so she made a taste-a-lemon face at him. Frightened, he screamed into her face. I swung the cart quickly around and held his head in my arms while he fretted and I cooed. Evil Lady kept giving pointed looks to the cashier as she checked out. I ignored Evil Lady's attempts to make eye contact with me.

Then, thankfully, her transaction was over and we were at the register. But as she was leaving, she just had to turn around one more time to again make that face at my child. I swear I just thought it, but apparently it popped out of my mouth. I had no expression on my face, no tone to my voice, just two little words hanging in the air in front of me. "Old bag."

oops
interjection
Used to express acknowledgement of a minor accident, blunder, or mistake.
"oops." The American Heritage® Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. Answers.com 06 May. 2006. http://www.answers.com/topic/oops-1