Meaning: An incentive, stimulus, to elicit or accelerate a response or an action. (Idiom).
Translation: Incentivo o estimulo.
☞ Pronunciation: ´´a shat indi arm´´
This expression derives from the invigorating effect of injecting drugs. A shot is of course US slang for an injection, either of a narcotic or medicinal drug. That term has been in use since around the beginning of the 20th century. http://www.phrases.org.uk/meanings/318925.html
The banks can give local residents a shot in the arm to boost local economy.
A shot in the arm