Gumbi gumbi means: A shrub or small tree, , growing in inland Australia, used by Aboriginal peoples for food and medicine.. It is mainly Australian English and may not be understood outside that context. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. This is a food-related word and harmless in itself. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.