1. The line you get in that is always deceptively long, for instance when you get in the line that looks the shortest at the checkout at the grocery store, and an old senile woman is bagging so it takes you 10 extra minutes.
2. This can also be used to describe a line that is moving way faster than you thought, however negative connotations are implied.
"Wow what a deceptiline, we got into the fireworks store in no time"