Trou means: An informal shortening of 'trousers,' used in New Zealand, the US, and in the specific context of rowing. In rowing, 'trous' or 'trou' refers to the tight spandex shorts worn during training and. It is mainly New Zealand 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. It is sporting vocabulary and harmless in itself.