1. （初到某地或初出茅庐却）自命不凡的家伙
You can refer to someone as an upstart when they behave as if they are important, but you think that they are too new in a place or job to be treated as important.

1. 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 upright

Synonym: kip

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

Synonym: parvenunouveau-richearriviste

3. an arrogant or presumptuous person