upstart

Concise Oxford English Dictionary © 2008 Oxford University Press:
upstart/ˈʌpstɑːt/

▶noun

• 1 derogatory a person who has risen suddenly to prominence, especially one who behaves arrogantly.

• 2 Gymnastics a series of movements by which a gymnast swings to a position supported by their arms above a bar, especially at the start of a routine.