BFG, the /ˌbi ef ˈdʒiː/
a children's story by Roald Dahl about a giant (=extremely large tall man) who is called the BFG because he is a big friendly giant and is not bad or frightening like most giants

[TahlilGaran] Dictionary of Contemporary English ▲

BFG
Big Freakin' Guitar (polite form) 
Big Freaking Gun (polite form) 
Big Friendly Giant

[TahlilGaran] Acronyms and Abbreviations Dictionary ▲