Iwi means: An extended group of Maori kin groups or families, sharing common ancestry; a tribe. (An iwi is smaller than a waka and larger than a hapu.).. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. 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.