Acela mode means: The mental and physical operating state of someone fully inhabiting the DC/NYC power corridor lifestyle: laptop open, policy brief bookmarked, coffee in a branded mug, using phrases like 'bandwidth'. 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.