I don’t know why oap isn’t a bona fide word by now. I bet you’ve all used the word at least once in the past 24 hours (unless you’re the sort of internetter who hasn’t seen another living being in the last 24 hours)…

oap (interjection): acknowledging a minor minor mistake; a word that I use 17 times a day, and hear coming out of other peoples’ mouths almost as often but that isn’t in the dictionary because one says it only when trying not to be noticed, and thus no one notices it as a word; minuscule form of oops, used when an oops might otherwise be appropriate, but you’re too busy concentrating on being an oaf to come up with anything much more than a random embarrassed grunt of a noise (possible origin of the word — a combination of oaf and oops?); an exclamation similar to eep, but much less urgent and sans any actual shock or fear, or for that matter, an exclamatory tone of voice; the proper, polite vocalization upon almost (but not quite) running into someone in an office hallway or grocery store