Bus or train (5)
I believe the answer is:
coach
I believe this is a double definition.
'bus' is the first definition.
('coach' can be a synonym of 'bus')
'train' is the second definition.
('coach' can be a synonym of 'train')
'or' is the link.
(Other definitions for coach that I've seen before include "Trainer and train carriage" , "Trainer and bus" , "Tutor" , "Railway carriage or sports instructor" , "Train the bus" .)