Someone who has a characteristic so freaking fantastic that it makes them instantly cool. In other words, the one attribute over shadows all other shortcomings.
When a person's Instagram photo is so attractive, it gives you a semi-erection, one that's enough for you to question your existence and wonder why you'll never get with someone like that.
Kids that go Scene overnight and claim to be ohh so hardcore and follow other instacore trens. like listening to shitty local bands and doing their hair all the wrong ways. These kids think they are really cool, but are usually reminded by everyone else how lame they are.
When you add your friend's Instagram story to your Instagram story, and your friend adds your Instagram-story-addition to their Instagram story, creating a possible infinite loop of Instagram stories.
When you stalk your boyfriend's ex-girlfriend on Instagram and accidentally like her photo and unlike it in a heartbeat. However, she sees that happening.
"My ex-boyfriend's current girlfriend had an Instaoops moment and she thought she got away with it."