0 a children's bicycle designed to attach to the back of an adult's bicycle:
1 someone who goes somewhere or does something with another person or other people, especially when they has not been invited:
Unimpressed by the prospect of a teenage tagalong, the cyclists promply leave him behind at mile 2.
Katie is the tagalong who refuses to be ignored or excluded.
My husband can connect the tagalong and trailer to his bike to get the kids home.
He looked over his shoulder at the tagalong and shouted, "You OK, Max?"
