Green’s Dictionary of Slang

(S.Afr.) South African version of the yuppie n.

1989		Style Feb. 125: Guava: There seems to be some confusion about this demographic ugliness. Some say it stands for Growing Up And Very Ambitious, others say Grown Up And Very Ambitious and a third opinion exists that the little brutes are not Very Ambitious at all, but just Vaguely Ambitious ... There are a number of professions and careers to pursue which would give the aspirant Guava sufficient velocity to be catapulted into the limelight [DSAE].
1992		Scope 1 Nov. 51 : Besides being a Guava (Growing up and very ambitious) Wayne’s also a bit of a daredevil [DSAE].