(transport, civil engineering) A tunnel driven through a pass at fairly high altitude to minimize the length of tunnel required, at the cost of requiring steeper and more winding routes up to each end of the tunnel.

(transport, civil engineering) A culmination tunnel.

(US) The screaming crowds near Wellesley College during the annual Boston Marathon.

A kind of motor vehicle road rally for high-performance vehicles, emphasizing recreational driving in a group, especially through tunnels.

(idiomatic) A better situation after long hardship. / A vision of a bright light, surrounded by darkness, seen by a dying person

(neurology) form of repetitive stress injury caused by compression of the median nerve travelling through the carpal tunnel.

(business) The application of a rigorous testing regime to a new corporate idea, structure or project to see if it is viable and fit for purpose.

(rail transport) A railway station and junction in Monmouthshire, Wales, on the west side of the Severn Tunnel, which serves the village of Rogiet (OS grid ref ST4687).

plural of tunnel boring machine

(engineering) A large machine used to excavate tunnels with a circular cross section.