Boludo/a is one of those wonderful words in Argentine Spanish that just does not have an English translation to give the meaning justice. The word signifies many different things, sometimes possessing a derogatory connotation, other times used in an affectionate banter among friends (for more decent definitions, check out urbandictionary.
The word can be used as a noun, verb, adjective or all of the above to mean:
1. Dumbass: “That boluda joined the Sarah Palin is my hero group on facebook”
2. Dude: “Boludo, what did you do last night?”
3. Fuckin’ around (not in a sexual manner): I spent all day boludeando (deriving from the verb, boludear) on wikipedia.
4. Douchebag: What a boludo, has a big tattoo that says “AWSOME” across his forearm
Best to watch this commercial entitled “Qué Bolu (abbreviation)” that perfectly embodies the meaning of the word boludo.