(noun) Someone who acts like a gangster, but tries to hard. Ganka's are usually seen wearing work boots, a shirt that hangs to their knees, and wear pants that are 10 sizes too big without a belt.
David: I havn't seen a ganka today.
Andrew: Maybe that's why the stores so busy!
Ruby Kurosawa's (From Love Live!! Sunshine) catchphrase.
It's supposed to be a joke on words because ganbaru (roughly) means 'Do your best' in Japanese and her name is 'Ruby' so it becomes 'ganbaruby' which means 'Do your rubesty'!
Love Live fan #1: I have two tests coming up..
Love Live fan #2: Don't worry! Ganbaruby!