People might describe you as uppity if you're bossy and stuck-up. An uppity waiter at a fancy restaurant might look visibly disgusted if you wear your oldest sneakers and your overalls to dinner.
Someone who's a snob or who acts like a pompous know-it-all deserves to be described as uppity. It's an informal way to talk about a snooty or arrogant person, and it first appeared in African American English in the nineteenth century. The initial published use of uppity was in "Uncle Remus," a collection of African American folk stories adapted by a white journalist in 1881.