Meaning

noun an arrogant or presumptuous person

noun a person who has suddenly risen to a higher economic status but has not gained social acceptance of others in that class

noun a gymnastic exercise performed starting from a position with the legs over the upper body and moving to an erect position by arching the back and swinging the legs out and down while forcing the chest

originFrom Middle English upstarten, upsterten, equivalent to up- + start.

Etymology from Wiktionary, CC BY-SA 3.0