derp
n. countable C2 Proficiency derp
n. a word used to describe a silly mistake or a foolish person. It is often used online when someone does something clumsy or looks a bit strange.
n. a foolish or silly person, or a mistake resulting from a lack of attention. Often used to describe a facial expression that appears cross-eyed or vacant; highly informal and common in internet subcultures.
I had a total derp moment and forgot my own phone number.
The photo would have been perfect, but my dog had a major derp and stuck his tongue out right as the shutter clicked.
Usage
Often used as an interjection to acknowledge one's own stupidity or as a noun to label a clumsy act.