Biballs means: Loose-fitting pants with supporting cross-straps and a panel of material in the chest (called a bib), often associated with farm work.. It is mainly Canadian 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. 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.