(sense 1): Interjection signifying pain, weariness, disgust, resignation, etc. Very often part of oy vey or oy vas mir. Compare to English Jeez. (from Yiddish "oy", probably from old German; probably cognate to English "oh").

(sense 2): Interjection signifying annoyance. Very similar to sense 1, but more annoyed than resigned. (Probably from Cockney accent of English "Hey".)

(sense 3) Greeting meaning "hello" or "Hi". (Probably from Cockney "hi").

1.) an expression of shock or amusement; oh my

an exclamation of suprise, dismay, confusion, or any other feeling (from Heberew)

word commonly used to express anger, frustration or complete disbelief in stupidity.

basically, the word "oy" is putting *smacks forehead* into a word.

Used when you or someone else does something stupid. It also can be used if one is annoyed, disgusted, bored, surprised, or in pain. Or just for the thrill of saying something nobody else says.

something to say to get attention when everyone is talking over you

"the funniest word ever" according to Lorelai on Gilmore Girls.