squirrel

¿Qué sería esto en español?

Squirrel
A nickname often given to a rookie firefighter who tends to be over zealous.

They typically believe they know more than they actually do, and relish in telling others the stories of there heroism, which are almost always exaggerations of the truth.
Did you meet the new guy? He was talking about that box the other day. To hear him tell it, you'd think he drove the engine there, and put the thing out himself. What a squirrel.