People usually in their late teens or younger stages of adulthood who base their social identity around counter-culture, alternative music, the arts and social justice.
Hipsters are often seen as pretentious due to carrying with them an air of superiority while having achieved little of note personally. They like the idea of academia but contribute nothing much of value in the academic world and they like the idea of a social revolution but are generally unwilling to risk their usually comfortable lifestyles to achieve this.
Hipster identity is usually based around rejection of the mainstream and ironic use of mainstream fashions that have fallen out of style. Certain types of clothing and fashion accessories have actually come back into style as a result of popularisation by hipsters - they fail to see the irony in this.
Look at the top definition for hipsters on Urban Dictionary. How much of a pretentious ass does someone have to be to write paragraph after paragraph of such self-aggrandising nonsense?
A young adult who's major accomplishment in life is considering themselves "cooler" than their surrounding society.
Hipster: you listen to the mainstream radio? Pffft, you're one of the sheeple.
Me: Wow, you're so much cooler than me. Congratulations. What an incredibly important accomplishment!
1. An arrogant ass-sucker who could find irony in a blowjob, but could not find a way out of his or her own sphincter
2. Someone who mistakenly considers himself or herself cooler (i.e. more "hip"), smarter, and more open-minded than others due to a misplaced sense of self-worth; also likes to refer to himself or herself as a "hipster"
Examples
1. Jason's hipster girlfriend gave him oral sex, then found it ironic that his jizz tasted like the food he had for dinner.
2. While sniffing her anus to confirm that her shit did not indeed stink, Jason's hipster girlfriend managed to stick part of her face into her butt. The paramedics had to come dislodge her head from her ass.
3. Some hipster was preaching about the differences between Plato and Aristotle on the street-corner. He had never read the works of Plato, nor of Aristotle, but he was convinced of his authority on the matter because he had good grades in classes other than philosophy and he wore hipster glasses with a hipster hairstyle.
A pretentious person who is decadent and weak through self-indulgences and makes attempts to 'stand out' or appear different from what they perceive to be the average person by wearing ostentatious clothing, and doing pretty much anything that calls attention to themselves. They are usually progressives.
He is such a hipster.
Hey! Look at that hipster over yonder! He (She) is listening to music, therefore, he (she) must truly enjoy it, because it is also creatively expressed through his (her) fashion and sweet, sweet dance (or lack of) dance moves.
A hipster is a gentrified hippy
Those hipsters look so skanky but smell like organic lavender oil
Not different enough to be interesting, but just different enough to be annoying.
My slightly too small font is so hipster.