Piggy-wig means: A sweet, infantile term for a pig - the kind used by parents, grandparents, and anyone trying to make a toddler giggle. 'Piggy-wig' has the round, warm sound of nursery English, making a barnyard. 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.