An exclamation that, when uttered in conjunction with taking an object, immediately transfers ownership from the original owner to the person using the wordregardless of previous property rights.
Though I cherished my automobile, I had to purchase a new one when my second cousin came up from behind me and politely exclaimed, "Yoink" while taking my car keys.
A sound effect created by Don Martin of Mad Magazine used to indicate the rapid pulling or removal of an object, much like 'Pow" or "Bam" would indicate a punch or hard hit in a Batman comic. Later used numerous times by characters on The Simpsons to indicate quick grabbing of something belonging to others.
"It's mine", said Bart. "No, it's mine", said Lisa. "Yoink!". Now it's mine, said Marge.